Account for fixed positioning once when computing parent offset

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 <algorithm>
 #include <set>
 
 #include "cc/animation/layer_animation_controller.h"
@@ skipping 8886 matching lines @@
   rotated->AddChild(surface);
   surface->AddChild(container);
   surface->AddChild(box);
 
   scoped_ptr<FakeLayerTreeHost> host(CreateFakeLayerTreeHost());
   host->SetRootLayer(root);
 
   ExecuteCalculateDrawProperties(root.get());
 }
 
+TEST_F(LayerTreeHostCommonTest, OnlyApplyFixedPositioningOnce) {
+  gfx::Transform identity;
+  gfx::Transform translateZ;

[ajuma, 2015/03/20 18:15:34]

nit: translate_z

[Ian Vollick, 2015/03/20 20:23:20]

Done.

+  translateZ.Translate3d(0, 0, 10);
+
+  scoped_refptr<Layer> root = Layer::Create();
+  SetLayerPropertiesForTesting(root.get(), identity, gfx::Point3F(),
+                               gfx::PointF(), gfx::Size(800, 800), true, false);
+  root->SetIsContainerForFixedPositionLayers(true);
+
+  scoped_refptr<Layer> frame_clip = Layer::Create();
+  SetLayerPropertiesForTesting(frame_clip.get(), translateZ, gfx::Point3F(),
+                               gfx::PointF(500, 100), gfx::Size(100, 100), true,
+                               false);
+  frame_clip->SetMasksToBounds(true);
+
+  scoped_refptr<LayerWithForcedDrawsContent> fixed =
+      make_scoped_refptr(new LayerWithForcedDrawsContent());
+  SetLayerPropertiesForTesting(fixed.get(), identity, gfx::Point3F(),
+                               gfx::PointF(), gfx::Size(1000, 1000), true,
+                               false);
+
+  LayerPositionConstraint constraint;
+  constraint.set_is_fixed_position(true);
+  fixed->SetPositionConstraint(constraint);
+
+  root->AddChild(frame_clip);
+  frame_clip->AddChild(fixed);
+
+  scoped_ptr<FakeLayerTreeHost> host(CreateFakeLayerTreeHost());
+  host->SetRootLayer(root);
+
+  ExecuteCalculateDrawProperties(root.get());

[ajuma, 2015/03/20 18:15:35]

It'd be good to add 'EXPECT' lines here so this continues to be a meaningful
test once property trees are on by default.

[Ian Vollick, 2015/03/20 20:23:20]

Done.

+}
+
 }  // namespace
 }  // namespace cc