Support bottom-right anchored fixed-position elements during a pinch gesture

cc/layers/layer_position_constraint_unittest.cc

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cc/layers/layer_position_constraint.h"
+
+#include "cc/layers/layer_impl.h"
+#include "cc/test/fake_impl_proxy.h"
+#include "cc/test/fake_layer_tree_host_impl.h"
+#include "cc/test/geometry_test_utils.h"
+#include "cc/trees/layer_tree_host_common.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cc {
+namespace {
+
+template <typename LayerType>
+void SetLayerPropertiesForTestingInternal(

[shawnsingh, 2013/04/04 10:15:14]

Since this is only used by LayerImpl side, let's get rid of this wrapper and
combine it with SetLayerPropertiesForTesting below.

Also, we should make a note to follow-up: the occlusion tracker has a similar
function, and we should consider moving all this to test/layer_test_common in a
separate clean-up patch.

[trchen, 2013/04/04 11:18:05]

Done.
Agree.

+    LayerType* layer,
+    const gfx::Transform& transform,
+    const gfx::Transform& sublayer_transform,
+    gfx::PointF anchor,
+    gfx::PointF position,
+    gfx::Size bounds,
+    bool preserves3d) {
+  layer->SetTransform(transform);
+  layer->SetSublayerTransform(sublayer_transform);
+  layer->SetAnchorPoint(anchor);
+  layer->SetPosition(position);
+  layer->SetBounds(bounds);
+  layer->SetPreserves3d(preserves3d);
+}
+
+void SetLayerPropertiesForTesting(LayerImpl* layer,
+                                  const gfx::Transform& transform,
+                                  const gfx::Transform& sublayer_transform,
+                                  gfx::PointF anchor,
+                                  gfx::PointF position,
+                                  gfx::Size bounds,
+                                  bool preserves3d) {
+  SetLayerPropertiesForTestingInternal<LayerImpl>(layer,
+                                                  transform,
+                                                  sublayer_transform,
+                                                  anchor,
+                                                  position,
+                                                  bounds,
+                                                  preserves3d);
+  layer->SetContentBounds(bounds);
+}
+
+void ExecuteCalculateDrawProperties(LayerImpl* root_layer,
+                                    float device_scale_factor,
+                                    float page_scale_factor,
+                                    bool can_use_lcd_text) {
+  gfx::Transform identity_matrix;
+  std::vector<LayerImpl*> dummy_render_surface_layer_list;
+  int dummy_max_texture_size = 512;
+  gfx::Size device_viewport_size =
+      gfx::Size(root_layer->bounds().width() * device_scale_factor,
+                root_layer->bounds().height() * device_scale_factor);
+
+  // We are probably not testing what is intended if the root_layer bounds are
+  // empty.
+  DCHECK(!root_layer->bounds().IsEmpty());
+  LayerTreeHostCommon::CalculateDrawProperties(root_layer,
+                                               device_viewport_size,
+                                               device_scale_factor,
+                                               page_scale_factor,
+                                               dummy_max_texture_size,
+                                               can_use_lcd_text,
+                                               &dummy_render_surface_layer_list,
+                                               false);
+}
+
+template <class LayerType>
+void ExecuteCalculateDrawProperties(LayerType* root_layer) {

[shawnsingh, 2013/04/04 10:15:14]

And this probably doesn't need to be templated here.

[trchen, 2013/04/04 11:18:05]

Done.

+  ExecuteCalculateDrawProperties(root_layer, 1.f, 1.f, false);
+}
+
+class LayerPositionConstraintTest : public testing::Test {
+ public:
+  LayerPositionConstraintTest()
+      : host_impl_(&proxy_) {
+    root_ = CreateTreeForTest();
+    fixed_to_top_left_.set_is_fixed_position(true);
+    fixed_to_bottom_right_.set_is_fixed_position(true);
+    fixed_to_bottom_right_.set_is_fixed_to_right_edge(true);
+    fixed_to_bottom_right_.set_is_fixed_to_bottom_edge(true);
+  }
+
+  scoped_ptr<LayerImpl> CreateTreeForTest() {
+    scoped_ptr<LayerImpl> root =
+        LayerImpl::Create(host_impl_.active_tree(), 1);
+    scoped_ptr<LayerImpl> child =
+        LayerImpl::Create(host_impl_.active_tree(), 2);
+    scoped_ptr<LayerImpl> grand_child =
+        LayerImpl::Create(host_impl_.active_tree(), 3);
+    scoped_ptr<LayerImpl> great_grand_child =
+        LayerImpl::Create(host_impl_.active_tree(), 4);
+
+    gfx::Transform IdentityMatrix;
+    gfx::PointF anchor;
+    gfx::PointF position;
+    gfx::Size bounds(100, 100);
+    SetLayerPropertiesForTesting(root.get(),
+                                 IdentityMatrix,
+                                 IdentityMatrix,
+                                 anchor,
+                                 position,
+                                 bounds,
+                                 false);
+    SetLayerPropertiesForTesting(child.get(),
+                                 IdentityMatrix,
+                                 IdentityMatrix,
+                                 anchor,
+                                 position,
+                                 bounds,
+                                 false);
+    SetLayerPropertiesForTesting(grand_child.get(),
+                                 IdentityMatrix,
+                                 IdentityMatrix,
+                                 anchor,
+                                 position,
+                                 bounds,
+                                 false);
+    SetLayerPropertiesForTesting(great_grand_child.get(),
+                                 IdentityMatrix,
+                                 IdentityMatrix,
+                                 anchor,
+                                 position,
+                                 bounds,
+                                 false);
+
+    grand_child->AddChild(great_grand_child.Pass());
+    child->AddChild(grand_child.Pass());
+    root->AddChild(child.Pass());
+
+    return root.Pass();
+  }
+ protected:
+  FakeImplProxy proxy_;
+  FakeLayerTreeHostImpl host_impl_;
+  scoped_ptr<LayerImpl> root_;
+
+  LayerPositionConstraint fixed_to_top_left_;
+  LayerPositionConstraint fixed_to_bottom_right_;
+};
+
+TEST_F(LayerPositionConstraintTest,
+     ScrollCompensationForFixedPositionLayerWithDirectContainer) {
+  // This test checks for correct scroll compensation when the fixed-position
+  // container is the direct parent of the fixed-position layer.
+  LayerImpl* child = root_->children()[0];
+  LayerImpl* grand_child = child->children()[0];
+
+  child->SetIsContainerForFixedPositionLayers(true);
+  grand_child->SetPositionConstraint(fixed_to_top_left_);
+
+  // Case 1: scroll delta of 0, 0
+  child->SetScrollDelta(gfx::Vector2d(0, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  gfx::Transform expected_child_transform;
+  gfx::Transform expected_grand_child_transform = expected_child_transform;
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 2: scroll delta of 10, 10
+  child->SetScrollDelta(gfx::Vector2d(10, 10));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Here the child is affected by scroll delta, but the fixed position
+  // grand_child should not be affected.
+  expected_child_transform.MakeIdentity();
+  expected_child_transform.Translate(-10.0, -10.0);
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 3: fixed-container size delta of 20, 20
+  child->SetFixedContainerSizeDelta(gfx::Vector2d(20, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Top-left fixed-position layer should not be affected by container size.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 4: Bottom-right fixed-position layer.
+  grand_child->SetPositionConstraint(fixed_to_bottom_right_);
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Bottom-right fixed-position layer moves as container resizes.
+  expected_grand_child_transform.Translate(20.0, 20.0);
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+}
+
+TEST_F(LayerPositionConstraintTest,
+     ScrollCompensationForFixedPositionLayerWithTransformedDirectContainer) {
+  // This test checks for correct scroll compensation when the fixed-position
+  // container is the direct parent of the fixed-position layer, but that
+  // container is transformed.  In this case, the fixed position element
+  // inherits the container's transform, but the scroll delta that has to be
+  // undone should not be affected by that transform.
+  //
+  // gfx::Transforms are in general non-commutative; using something like a

[shawnsingh, 2013/04/04 10:15:14]

gfx::Transforms --> transforms.  I think this was a search-replace typo of mine
from a few months ago, but it's a good opportunity to fix it =)

[trchen, 2013/04/04 11:18:05]

Done.

+  // non-uniform scale helps to verify that translations and non-uniform scales
+  // are applied in the correct order.
+  LayerImpl* child = root_->children()[0];
+  LayerImpl* grand_child = child->children()[0];
+
+  // This scale will cause child and grand_child to be effectively 200 x 800
+  // with respect to the render target.
+  gfx::Transform non_uniform_scale;
+  non_uniform_scale.Scale(2.0, 8.0);
+  child->SetTransform(non_uniform_scale);
+
+  child->SetIsContainerForFixedPositionLayers(true);
+  grand_child->SetPositionConstraint(fixed_to_top_left_);
+
+  // Case 1: scroll delta of 0, 0
+  child->SetScrollDelta(gfx::Vector2d(0, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  gfx::Transform expected_child_transform;
+  expected_child_transform.PreconcatTransform(non_uniform_scale);
+
+  gfx::Transform expected_grand_child_transform = expected_child_transform;
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 2: scroll delta of 10, 20
+  child->SetScrollDelta(gfx::Vector2d(10, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // The child should be affected by scroll delta, but the fixed position
+  // grand_child should not be affected.
+  expected_child_transform.MakeIdentity();
+  expected_child_transform.Translate(-10.0, -20.0);  // scroll delta
+  expected_child_transform.PreconcatTransform(non_uniform_scale);
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 3: fixed-container size delta of 20, 20
+  child->SetFixedContainerSizeDelta(gfx::Vector2d(20, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Top-left fixed-position layer should not be affected by container size.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 4: Bottom-right fixed-position layer.
+  grand_child->SetPositionConstraint(fixed_to_bottom_right_);
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Bottom-right fixed-position layer moves as container resizes.
+  expected_grand_child_transform.Translate(20.0, 20.0);

[shawnsingh, 2013/04/04 10:15:14]

Something isn't right here, but I can't explain why this test would be passing
even though it's wrong.

The way we're defining our expected transform:

scrollDeltaCompensation * nonUniformScale * sizeDeltaCompensation

but the correct expected transform should be:

scrollDeltaCompensation * sizeDeltaCompensation * nonUniformScale.

the whole point of choosing nonUniformScale was to make sure it is not
commutative, and yet somehow this test is passing with the backwards expected
transform sequence =)

Do you see what I mean?  Unfortunately, we need to investigate this before
landing, and get a solid explanation and fix.

By the way, this issue is actually true of all "case 4" tests here.  It just so
happens that for the simpler tests, the additional matrix does not exist in the
sequence (the nonUniformScale in this case), so it happens to be correct.

[trchen, 2013/04/04 11:18:05]

There is no sizeDeltaCompensation in the tests at all.

I never meant to verify the size delta compensation matrix in the first place.
Doing that falls exactly into the problem of "putting a test value just because
that's what this patch outputs". The test shouldn't know too much about internal
computation in LayerTreeHostCommon.

Instead, I did all the values by hand, by drawing the layers on a paper and
figure out the bottom-right offset in the local space. By comparing the output
from a different method, actually I get more confidence that the patch is doing
the right thing here.

Anyway I agree that plugging mysterious values everywhere makes the tests
difficult to read and maintain if we ever change the tests later. I'll try to
make it looks less of a puzzle.
This works correctly because .Translate is a preconcat. No matter what transform
is applied on the container, in local space the fixed-position layer moves exact
sizeDelta (given that no transformation in between). If you want it to be a
concat, then the translation offset should become (40, 160).

+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+}
+
+TEST_F(LayerPositionConstraintTest,
+     ScrollCompensationForFixedPositionLayerWithDistantContainer) {
+  // This test checks for correct scroll compensation when the fixed-position
+  // container is NOT the direct parent of the fixed-position layer.
+  LayerImpl* child = root_->children()[0];
+  LayerImpl* grand_child = child->children()[0];
+  LayerImpl* great_grand_child = grand_child->children()[0];
+
+  child->SetIsContainerForFixedPositionLayers(true);
+  grand_child->SetPosition(gfx::PointF(8.f, 6.f));
+  great_grand_child->SetPositionConstraint(fixed_to_top_left_);
+
+  // Case 1: scroll delta of 0, 0
+  child->SetScrollDelta(gfx::Vector2d(0, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  gfx::Transform expected_child_transform;
+  gfx::Transform expected_grand_child_transform;
+  expected_grand_child_transform.Translate(8.0, 6.0);
+
+  gfx::Transform expected_great_grand_child_transform =
+      expected_grand_child_transform;
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 2: scroll delta of 10, 10
+  child->SetScrollDelta(gfx::Vector2d(10, 10));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Here the child and grand_child are affected by scroll delta, but the fixed
+  // position great_grand_child should not be affected.
+  expected_child_transform.MakeIdentity();
+  expected_child_transform.Translate(-10.0, -10.0);
+  expected_grand_child_transform.MakeIdentity();
+  expected_grand_child_transform.Translate(-2.0, -4.0);
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 3: fixed-container size delta of 20, 20
+  child->SetFixedContainerSizeDelta(gfx::Vector2d(20, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Top-left fixed-position layer should not be affected by container size.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 4: Bottom-right fixed-position layer.
+  great_grand_child->SetPositionConstraint(fixed_to_bottom_right_);
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Bottom-right fixed-position layer moves as container resizes.
+  expected_great_grand_child_transform.Translate(20.0, 20.0);
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+}
+
+TEST_F(LayerPositionConstraintTest,
+     ScrollCompensationForFixedPositionLayerWithDistantContainerAndTransforms) {
+  // This test checks for correct scroll compensation when the fixed-position
+  // container is NOT the direct parent of the fixed-position layer, and the
+  // hierarchy has various transforms that have to be processed in the correct
+  // order.
+  LayerImpl* child = root_->children()[0];
+  LayerImpl* grand_child = child->children()[0];
+  LayerImpl* great_grand_child = grand_child->children()[0];
+
+  gfx::Transform rotation_about_z;
+  rotation_about_z.RotateAboutZAxis(90.0);
+
+  child->SetIsContainerForFixedPositionLayers(true);
+  child->SetTransform(rotation_about_z);
+  grand_child->SetPosition(gfx::PointF(8.f, 6.f));
+  grand_child->SetTransform(rotation_about_z);
+  // great_grand_child is positioned upside-down with respect to the render
+  // target.
+  great_grand_child->SetPositionConstraint(fixed_to_top_left_);
+
+  // Case 1: scroll delta of 0, 0
+  child->SetScrollDelta(gfx::Vector2d(0, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  gfx::Transform expected_child_transform;
+  expected_child_transform.PreconcatTransform(rotation_about_z);
+
+  gfx::Transform expected_grand_child_transform;
+  expected_grand_child_transform.PreconcatTransform(
+      rotation_about_z);  // child's local transform is inherited
+  // translation because of position occurs before layer's local transform.
+  expected_grand_child_transform.Translate(8.0, 6.0);
+  expected_grand_child_transform.PreconcatTransform(
+      rotation_about_z);  // grand_child's local transform
+
+  gfx::Transform expected_great_grand_child_transform =
+      expected_grand_child_transform;
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 2: scroll delta of 10, 20
+  child->SetScrollDelta(gfx::Vector2d(10, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Here the child and grand_child are affected by scroll delta, but the fixed
+  // position great_grand_child should not be affected.
+  expected_child_transform.MakeIdentity();
+  expected_child_transform.Translate(-10.0, -20.0);  // scroll delta
+  expected_child_transform.PreconcatTransform(rotation_about_z);
+
+  expected_grand_child_transform.MakeIdentity();
+  expected_grand_child_transform.Translate(
+      -10.0, -20.0);      // child's scroll delta is inherited
+  expected_grand_child_transform.PreconcatTransform(
+      rotation_about_z);  // child's local transform is inherited
+  // translation because of position occurs before layer's local transform.
+  expected_grand_child_transform.Translate(8.0, 6.0);
+  expected_grand_child_transform.PreconcatTransform(
+      rotation_about_z);  // grand_child's local transform
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 3: fixed-container size delta of 20, 20
+  child->SetFixedContainerSizeDelta(gfx::Vector2d(20, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Top-left fixed-position layer should not be affected by container size.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 4: Bottom-right fixed-position layer.
+  great_grand_child->SetPositionConstraint(fixed_to_bottom_right_);
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Bottom-right fixed-position layer moves as container resizes.
+  expected_great_grand_child_transform.Translate(20.0, -20.0);

[shawnsingh, 2013/04/04 10:15:14]

this comment also applies to all tests, but this is the first test where the
issue is obvious.

I wondered why it's a translation of +20, -20, the reason is hidden the way the
test is written - there are more transforms that need to be shown explicitly
here.

If we don't do that, we run the high risk of "putting a test value just because
that's what this patch outputs", and not really knowing to ourselves if it's
correct.  spelling out the transforms here will force us to make sure we
understand the scenario and expected result, in addition to testing the code.

+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+}
+
+TEST_F(LayerPositionConstraintTest,
+     ScrollCompensationForFixedPositionLayerWithMultipleScrollDeltas) {
+  // This test checks for correct scroll compensation when the fixed-position
+  // container has multiple ancestors that have nonzero scroll delta before
+  // reaching the space where the layer is fixed.  In this test, each scroll
+  // delta occurs in a different space because of each layer's local transform.
+  // This test checks for correct scroll compensation when the fixed-position
+  // container is NOT the direct parent of the fixed-position layer, and the
+  // hierarchy has various transforms that have to be processed in the correct
+  // order.
+  LayerImpl* child = root_->children()[0];
+  LayerImpl* grand_child = child->children()[0];
+  LayerImpl* great_grand_child = grand_child->children()[0];
+
+  gfx::Transform rotation_about_z;
+  rotation_about_z.RotateAboutZAxis(90.0);
+
+  child->SetIsContainerForFixedPositionLayers(true);
+  child->SetTransform(rotation_about_z);
+  grand_child->SetPosition(gfx::PointF(8.f, 6.f));
+  grand_child->SetTransform(rotation_about_z);
+  // great_grand_child is positioned upside-down with respect to the render
+  // target.
+  great_grand_child->SetPositionConstraint(fixed_to_top_left_);
+
+  // Case 1: scroll delta of 0, 0
+  child->SetScrollDelta(gfx::Vector2d(0, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  gfx::Transform expected_child_transform;
+  expected_child_transform.PreconcatTransform(rotation_about_z);
+
+  gfx::Transform expected_grand_child_transform;
+  expected_grand_child_transform.PreconcatTransform(
+      rotation_about_z);  // child's local transform is inherited
+  // translation because of position occurs before layer's local transform.
+  expected_grand_child_transform.Translate(8.0, 6.0);
+  expected_grand_child_transform.PreconcatTransform(
+      rotation_about_z);  // grand_child's local transform
+
+  gfx::Transform expected_great_grand_child_transform =
+      expected_grand_child_transform;
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 2: scroll delta of 10, 20
+  child->SetScrollDelta(gfx::Vector2d(10, 0));
+  grand_child->SetScrollDelta(gfx::Vector2d(5, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Here the child and grand_child are affected by scroll delta, but the fixed
+  // position great_grand_child should not be affected.
+  expected_child_transform.MakeIdentity();
+  expected_child_transform.Translate(-10.0, 0.0);  // scroll delta
+  expected_child_transform.PreconcatTransform(rotation_about_z);
+
+  expected_grand_child_transform.MakeIdentity();
+  expected_grand_child_transform.Translate(
+      -10.0, 0.0);        // child's scroll delta is inherited
+  expected_grand_child_transform.PreconcatTransform(
+      rotation_about_z);  // child's local transform is inherited
+  expected_grand_child_transform.Translate(-5.0,
+                                           0.0);  // grand_child's scroll delta
+  // translation because of position occurs before layer's local transform.
+  expected_grand_child_transform.Translate(8.0, 6.0);
+  expected_grand_child_transform.PreconcatTransform(
+      rotation_about_z);  // grand_child's local transform
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 3: fixed-container size delta of 20, 20
+  child->SetFixedContainerSizeDelta(gfx::Vector2d(20, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Top-left fixed-position layer should not be affected by container size.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 4: Bottom-right fixed-position layer.

[shawnsingh, 2013/04/04 10:15:14]

I feel like the case 3 and case 4 here are actually not very meaningful.  This
test case is about testing multiple scroll deltas in-between a fixed-position
element and its container.   By the definition of size deltas we won't ever have
that issue.  So instead of these additional no-op cases, perhaps we should have
a brief comment that mentions, "testing size-delta here is not meaningful since
we cannot have multiple size-deltas in the hierarchy."

+  great_grand_child->SetPositionConstraint(fixed_to_bottom_right_);
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Bottom-right fixed-position layer moves as container resizes.
+  expected_great_grand_child_transform.Translate(20.0, -20.0);
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+}
+
+TEST_F(LayerPositionConstraintTest,
+     ScrollCompensationForFixedPositionWithIntermediateSurfaceAndTransforms) {
+  // This test checks for correct scroll compensation when the fixed-position
+  // container contributes to a different render surface than the fixed-position
+  // layer. In this case, the surface draw transforms also have to be accounted
+  // for when checking the scroll delta.
+  LayerImpl* child = root_->children()[0];
+  LayerImpl* grand_child = child->children()[0];
+  LayerImpl* great_grand_child = grand_child->children()[0];
+
+  child->SetIsContainerForFixedPositionLayers(true);
+  grand_child->SetPosition(gfx::PointF(8.f, 6.f));
+  grand_child->SetForceRenderSurface(true);
+  great_grand_child->SetPositionConstraint(fixed_to_top_left_);
+  great_grand_child->SetDrawsContent(true);
+
+  gfx::Transform rotation_about_z;
+  rotation_about_z.RotateAboutZAxis(90.0);
+  grand_child->SetTransform(rotation_about_z);
+
+  // Case 1: scroll delta of 0, 0
+  child->SetScrollDelta(gfx::Vector2d(0, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  gfx::Transform expected_child_transform;
+  gfx::Transform expected_surface_draw_transform;
+  expected_surface_draw_transform.Translate(8.0, 6.0);
+  expected_surface_draw_transform.PreconcatTransform(rotation_about_z);
+  gfx::Transform expected_grand_child_transform;
+  gfx::Transform expected_great_grand_child_transform;
+  ASSERT_TRUE(grand_child->render_surface());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(
+      expected_surface_draw_transform,
+      grand_child->render_surface()->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 2: scroll delta of 10, 30
+  child->SetScrollDelta(gfx::Vector2d(10, 30));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Here the grand_child remains unchanged, because it scrolls along with the
+  // render surface, and the translation is actually in the render surface. But,
+  // the fixed position great_grand_child is more awkward: its actually being
+  // drawn with respect to the render surface, but it needs to remain fixed with
+  // resepct to a container beyond that surface. So, the net result is that,
+  // unlike previous tests where the fixed position layer's transform remains
+  // unchanged, here the fixed position layer's transform explicitly contains
+  // the translation that cancels out the scroll.
+  expected_child_transform.MakeIdentity();
+  expected_child_transform.Translate(-10.0, -30.0);  // scroll delta
+
+  expected_surface_draw_transform.MakeIdentity();
+  expected_surface_draw_transform.Translate(-10.0, -30.0);  // scroll delta
+  expected_surface_draw_transform.Translate(8.0, 6.0);
+  expected_surface_draw_transform.PreconcatTransform(rotation_about_z);
+
+  // The rotation and its inverse are needed to place the scroll delta
+  // compensation in the correct space. This test will fail if the
+  // rotation/inverse are backwards, too, so it requires perfect order of
+  // operations.
+  expected_great_grand_child_transform.MakeIdentity();
+  expected_great_grand_child_transform.PreconcatTransform(
+      Inverse(rotation_about_z));
+  // explicit canceling out the scroll delta that gets embedded in the fixed
+  // position layer's surface.
+  expected_great_grand_child_transform.Translate(10.0, 30.0);
+  expected_great_grand_child_transform.PreconcatTransform(rotation_about_z);
+
+  ASSERT_TRUE(grand_child->render_surface());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(
+      expected_surface_draw_transform,
+      grand_child->render_surface()->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 3: fixed-container size delta of 20, 20
+  child->SetFixedContainerSizeDelta(gfx::Vector2d(20, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Top-left fixed-position layer should not be affected by container size.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+
+  // Case 4: Bottom-right fixed-position layer.
+  great_grand_child->SetPositionConstraint(fixed_to_bottom_right_);
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Bottom-right fixed-position layer moves as container resizes.
+  expected_great_grand_child_transform.Translate(20.0, -20.0);

[shawnsingh, 2013/04/04 10:15:14]

same issue here, we need to see the spelled-out explicit seuqence of transforms
that would have given us this expected result.

+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+}
+
+TEST_F(LayerPositionConstraintTest,
+     ScrollCompensationForFixedPositionLayerWithMultipleIntermediateSurfaces) {
+  // This test checks for correct scroll compensation when the fixed-position
+  // container contributes to a different render surface than the fixed-position
+  // layer, with additional render surfaces in-between. This checks that the
+  // conversion to ancestor surfaces is accumulated properly in the final matrix
+  // transform.
+  LayerImpl* child = root_->children()[0];
+  LayerImpl* grand_child = child->children()[0];
+  LayerImpl* great_grand_child = grand_child->children()[0];
+
+  // Add one more layer to the test tree for this scenario.
+  {
+    gfx::Transform identity;
+    scoped_ptr<LayerImpl> fixed_position_child =
+        LayerImpl::Create(host_impl_.active_tree(), 5);
+    SetLayerPropertiesForTesting(fixed_position_child.get(),
+                                 identity,
+                                 identity,
+                                 gfx::PointF(),
+                                 gfx::PointF(),
+                                 gfx::Size(100, 100),
+                                 false);
+    great_grand_child->AddChild(fixed_position_child.Pass());
+  }
+  LayerImpl* fixed_position_child = great_grand_child->children()[0];
+
+  // Actually set up the scenario here.
+  child->SetIsContainerForFixedPositionLayers(true);
+  grand_child->SetPosition(gfx::PointF(8.f, 6.f));
+  grand_child->SetForceRenderSurface(true);
+  great_grand_child->SetPosition(gfx::PointF(40.f, 60.f));
+  great_grand_child->SetForceRenderSurface(true);
+  fixed_position_child->SetPositionConstraint(fixed_to_top_left_);
+  fixed_position_child->SetDrawsContent(true);
+
+  // The additional rotations, which are non-commutative with translations, help
+  // to verify that we have correct order-of-operations in the final scroll
+  // compensation.  Note that rotating about the center of the layer ensures we
+  // do not accidentally clip away layers that we want to test.
+  gfx::Transform rotation_about_z;
+  rotation_about_z.Translate(50.0, 50.0);
+  rotation_about_z.RotateAboutZAxis(90.0);
+  rotation_about_z.Translate(-50.0, -50.0);
+  grand_child->SetTransform(rotation_about_z);
+  great_grand_child->SetTransform(rotation_about_z);
+
+  // Case 1: scroll delta of 0, 0
+  child->SetScrollDelta(gfx::Vector2d(0, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  gfx::Transform expected_child_transform;
+
+  gfx::Transform expected_grand_child_surface_draw_transform;
+  expected_grand_child_surface_draw_transform.Translate(8.0, 6.0);
+  expected_grand_child_surface_draw_transform.PreconcatTransform(
+      rotation_about_z);
+
+  gfx::Transform expected_grand_child_transform;
+
+  gfx::Transform expected_great_grand_child_surface_draw_transform;
+  expected_great_grand_child_surface_draw_transform.Translate(40.0, 60.0);
+  expected_great_grand_child_surface_draw_transform.PreconcatTransform(
+      rotation_about_z);
+
+  gfx::Transform expected_great_grand_child_transform;
+
+  gfx::Transform expected_fixed_position_child_transform;
+
+  ASSERT_TRUE(grand_child->render_surface());
+  ASSERT_TRUE(great_grand_child->render_surface());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(
+      expected_grand_child_surface_draw_transform,
+      grand_child->render_surface()->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(
+      expected_great_grand_child_surface_draw_transform,
+      great_grand_child->render_surface()->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_fixed_position_child_transform,
+                                  fixed_position_child->draw_transform());
+
+  // Case 2: scroll delta of 10, 30
+  child->SetScrollDelta(gfx::Vector2d(10, 30));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  expected_child_transform.MakeIdentity();
+  expected_child_transform.Translate(-10.0, -30.0);  // scroll delta
+
+  expected_grand_child_surface_draw_transform.MakeIdentity();
+  expected_grand_child_surface_draw_transform.Translate(-10.0,
+                                                        -30.0);  // scroll delta
+  expected_grand_child_surface_draw_transform.Translate(8.0, 6.0);
+  expected_grand_child_surface_draw_transform.PreconcatTransform(
+      rotation_about_z);
+
+  // grand_child, great_grand_child, and great_grand_child's surface are not
+  // expected to change, since they are all not fixed, and they are all drawn
+  // with respect to grand_child's surface that already has the scroll delta
+  // accounted for.
+
+  // But the great-great grandchild, "fixed_position_child", should have a
+  // transform that explicitly cancels out the scroll delta.  The expected
+  // transform is: compound_draw_transform.Inverse() * translate(positive scroll
+  // delta) * compound_origin_transform from great_grand_childSurface's origin
+  // to the root surface.
+  gfx::Transform compound_draw_transform;
+  compound_draw_transform.Translate(8.0,
+                                    6.0);  // origin translation of grand_child
+  compound_draw_transform.PreconcatTransform(
+      rotation_about_z);                   // rotation of grand_child
+  compound_draw_transform.Translate(
+      40.0, 60.0);        // origin translation of great_grand_child
+  compound_draw_transform.PreconcatTransform(
+      rotation_about_z);  // rotation of great_grand_child
+
+  expected_fixed_position_child_transform.MakeIdentity();
+  expected_fixed_position_child_transform.PreconcatTransform(
+      Inverse(compound_draw_transform));
+  // explicit canceling out the scroll delta that gets embedded in the fixed
+  // position layer's surface.
+  expected_fixed_position_child_transform.Translate(10.0, 30.0);
+  expected_fixed_position_child_transform.PreconcatTransform(
+      compound_draw_transform);
+
+  ASSERT_TRUE(grand_child->render_surface());
+  ASSERT_TRUE(great_grand_child->render_surface());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(
+      expected_grand_child_surface_draw_transform,
+      grand_child->render_surface()->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(
+      expected_great_grand_child_surface_draw_transform,
+      great_grand_child->render_surface()->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_fixed_position_child_transform,
+                                  fixed_position_child->draw_transform());
+
+
+  // Case 3: fixed-container size delta of 20, 20
+  child->SetFixedContainerSizeDelta(gfx::Vector2d(20, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Top-left fixed-position layer should not be affected by container size.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_fixed_position_child_transform,
+                                  fixed_position_child->draw_transform());
+
+  // Case 4: Bottom-right fixed-position layer.
+  fixed_position_child->SetPositionConstraint(fixed_to_bottom_right_);
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Bottom-right fixed-position layer moves as container resizes.
+  expected_fixed_position_child_transform.Translate(-20.0, -20.0);

[shawnsingh, 2013/04/04 10:15:14]

and again here, same issue as above =)

+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_great_grand_child_transform,
+                                  great_grand_child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_fixed_position_child_transform,
+                                  fixed_position_child->draw_transform());
+}
+
+TEST_F(LayerPositionConstraintTest,
+     ScrollCompensationForFixedPositionLayerWithContainerLayerThatHasSurface) {
+  // This test checks for correct scroll compensation when the fixed-position
+  // container itself has a render surface. In this case, the container layer
+  // should be treated like a layer that contributes to a render target, and
+  // that render target is completely irrelevant; it should not affect the
+  // scroll compensation.
+  LayerImpl* child = root_->children()[0];
+  LayerImpl* grand_child = child->children()[0];
+
+  child->SetIsContainerForFixedPositionLayers(true);
+  child->SetForceRenderSurface(true);
+  grand_child->SetPositionConstraint(fixed_to_top_left_);
+  grand_child->SetDrawsContent(true);
+
+  // Case 1: scroll delta of 0, 0
+  child->SetScrollDelta(gfx::Vector2d(0, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  gfx::Transform expected_surface_draw_transform;
+  expected_surface_draw_transform.Translate(0.0, 0.0);
+  gfx::Transform expected_child_transform;
+  gfx::Transform expected_grand_child_transform;
+  ASSERT_TRUE(child->render_surface());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_surface_draw_transform,
+                                  child->render_surface()->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 2: scroll delta of 10, 10
+  child->SetScrollDelta(gfx::Vector2d(10, 10));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // The surface is translated by scroll delta, the child transform doesn't
+  // change because it scrolls along with the surface, but the fixed position
+  // grand_child needs to compensate for the scroll translation.
+  expected_surface_draw_transform.MakeIdentity();
+  expected_surface_draw_transform.Translate(-10.0, -10.0);
+  expected_grand_child_transform.MakeIdentity();
+  expected_grand_child_transform.Translate(10.0, 10.0);
+
+  ASSERT_TRUE(child->render_surface());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_surface_draw_transform,
+                                  child->render_surface()->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 3: fixed-container size delta of 20, 20
+  child->SetFixedContainerSizeDelta(gfx::Vector2d(20, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Top-left fixed-position layer should not be affected by container size.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 4: Bottom-right fixed-position layer.
+  grand_child->SetPositionConstraint(fixed_to_bottom_right_);
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Bottom-right fixed-position layer moves as container resizes.
+  expected_grand_child_transform.Translate(20.0, 20.0);
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+}
+
+TEST_F(LayerPositionConstraintTest,
+     ScrollCompensationForFixedPositionLayerThatIsAlsoFixedPositionContainer) {
+  // This test checks the scenario where a fixed-position layer also happens to
+  // be a container itself for a descendant fixed position layer. In particular,
+  // the layer should not accidentally be fixed to itself.
+  LayerImpl* child = root_->children()[0];
+  LayerImpl* grand_child = child->children()[0];
+
+  child->SetIsContainerForFixedPositionLayers(true);
+  grand_child->SetPositionConstraint(fixed_to_top_left_);
+
+  // This should not confuse the grand_child. If correct, the grand_child would
+  // still be considered fixed to its container (i.e. "child").
+  grand_child->SetIsContainerForFixedPositionLayers(true);
+
+  // Case 1: scroll delta of 0, 0
+  child->SetScrollDelta(gfx::Vector2d(0, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  gfx::Transform expected_child_transform;
+  gfx::Transform expected_grand_child_transform;
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 2: scroll delta of 10, 10
+  child->SetScrollDelta(gfx::Vector2d(10, 10));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Here the child is affected by scroll delta, but the fixed position
+  // grand_child should not be affected.
+  expected_child_transform.MakeIdentity();
+  expected_child_transform.Translate(-10.0, -10.0);
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 3: fixed-container size delta of 20, 20
+  child->SetFixedContainerSizeDelta(gfx::Vector2d(20, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Top-left fixed-position layer should not be affected by container size.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 4: Bottom-right fixed-position layer.
+  grand_child->SetPositionConstraint(fixed_to_bottom_right_);
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Bottom-right fixed-position layer moves as container resizes.
+  expected_grand_child_transform.Translate(20.0, 20.0);
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_child_transform,
+                                  child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+}
+
+TEST_F(LayerPositionConstraintTest,
+     ScrollCompensationForFixedPositionLayerThatHasNoContainer) {
+  // This test checks scroll compensation when a fixed-position layer does not
+  // find any ancestor that is a "containerForFixedPositionLayers". In this
+  // situation, the layer should be fixed to the viewport -- not the root_layer,
+  // which may have transforms of its own.
+  LayerImpl* child = root_->children()[0];
+  LayerImpl* grand_child = child->children()[0];
+
+  gfx::Transform rotation_by_z;
+  rotation_by_z.RotateAboutZAxis(90.0);
+
+  root_->SetTransform(rotation_by_z);
+  grand_child->SetPositionConstraint(fixed_to_top_left_);
+
+  // Case 1: root scroll delta of 0, 0
+  root_->SetScrollDelta(gfx::Vector2d(0, 0));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  gfx::Transform identity_matrix;
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(identity_matrix, child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(identity_matrix,
+                                  grand_child->draw_transform());
+
+  // Case 2: root scroll delta of 10, 10
+  root_->SetScrollDelta(gfx::Vector2d(10, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // The child is affected by scroll delta, but it is already implcitly
+  // accounted for by the child's target surface (i.e. the root render surface).
+  // The grand_child is not affected by the scroll delta, so its draw transform
+  // needs to explicitly inverse-compensate for the scroll that's embedded in
+  // the target surface.
+  gfx::Transform expected_grand_child_transform;
+  expected_grand_child_transform.PreconcatTransform(Inverse(rotation_by_z));
+  // explicit cancelling out the scroll delta that gets embedded in the fixed
+  // position layer's surface.
+  expected_grand_child_transform.Translate(10.0, 20.0);
+  expected_grand_child_transform.PreconcatTransform(rotation_by_z);
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(identity_matrix, child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+
+  // Case 3: fixed-container size delta of 20, 20
+  root_->SetFixedContainerSizeDelta(gfx::Vector2d(20, 20));
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Top-left fixed-position layer should not be affected by container size.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(identity_matrix, child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+
+  // Case 4: Bottom-right fixed-position layer.
+  grand_child->SetPositionConstraint(fixed_to_bottom_right_);
+  ExecuteCalculateDrawProperties(root_.get());
+
+  // Root layer is not the fixed-container anyway.
+  EXPECT_TRANSFORMATION_MATRIX_EQ(identity_matrix, child->draw_transform());
+  EXPECT_TRANSFORMATION_MATRIX_EQ(expected_grand_child_transform,
+                                  grand_child->draw_transform());
+}
+
+}  // namespace
+}  // namespace cc