Reland use screen space transform to compute translation

cc/trees/layer_tree_host_common_unittest.cc

 // Copyright 2011 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/trees/layer_tree_host_common.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <memory>
@@ skipping 6878 matching lines @@
   EXPECT_VECTOR2DF_EQ(expected_scroller_screen_space_transform_translation,
                       scroller_impl->ScreenSpaceTransform().To2dTranslation());
 
   gfx::Transform expected_scroll_child_screen_space_transform;
   expected_scroll_child_screen_space_transform.Translate(-5.3f, -9.3f);
   expected_scroll_child_screen_space_transform.RotateAboutYAxis(30);
   EXPECT_TRANSFORMATION_MATRIX_EQ(expected_scroll_child_screen_space_transform,
                                   scroll_child_impl->ScreenSpaceTransform());
 }
 
+TEST_F(LayerTreeHostCommonTest, NonFlatContainerForFixedPosLayer) {
+  scoped_refptr<Layer> root = Layer::Create();
+  scoped_refptr<Layer> container = Layer::Create();
+  scoped_refptr<Layer> scroller = Layer::Create();
+  scoped_refptr<Layer> fixed_pos = Layer::Create();
+
+  scroller->SetIsContainerForFixedPositionLayers(true);
+  root->AddChild(container);
+  container->AddChild(scroller);
+  scroller->AddChild(fixed_pos);
+  host()->SetRootLayer(root);
+
+  LayerPositionConstraint fixed_position;
+  fixed_position.set_is_fixed_position(true);
+  scroller->SetScrollClipLayerId(container->id());
+  fixed_pos->SetPositionConstraint(fixed_position);
+
+  root->SetBounds(gfx::Size(50, 50));
+  container->SetBounds(gfx::Size(50, 50));
+  scroller->SetBounds(gfx::Size(50, 50));
+  fixed_pos->SetBounds(gfx::Size(50, 50));
+
+  gfx::Transform rotate;
+  rotate.RotateAboutXAxis(20);
+  container->SetTransform(rotate);
+
+  ExecuteCalculateDrawProperties(root.get());
+  TransformTree& tree =
+      root->layer_tree_host()->property_trees()->transform_tree;
+  gfx::Transform transform;
+  tree.ComputeTranslation(fixed_pos->transform_tree_index(),
+                          container->transform_tree_index(), &transform);
+  EXPECT_TRUE(transform.IsIdentity());
+}
+
 TEST_F(LayerTreeHostCommonTest, ScrollSnappingWithFixedPosChild) {
   // This test verifies that a fixed pos child of a scrolling layer doesn't get
   // snapped to integer coordinates.
   //
   // + root
   //   + container
   //    + scroller
   //     + fixed_pos
   //
   scoped_refptr<Layer> root = Layer::Create();
@@ skipping 2803 matching lines @@
   EXPECT_EQ(scroll_child6.id, grand_child10->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, parent3->scroll_tree_index());
   EXPECT_EQ(scroll_child7.id, child8->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, parent4->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, child9->scroll_tree_index());
   EXPECT_EQ(scroll_root1.id, grand_child12->scroll_tree_index());
 }
 
 }  // namespace
 }  // namespace cc