Account for fixed positioning once when computing parent offset

cc/trees/layer_tree_host_common_unittest.cc

Index: cc/trees/layer_tree_host_common_unittest.cc
diff --git a/cc/trees/layer_tree_host_common_unittest.cc b/cc/trees/layer_tree_host_common_unittest.cc
index 0a51cccfc0b61706e26f37be82fb7f6ffd2afc85..d10668e956bc8ecfa845f39fa8be899fcdc46a61 100644
--- a/cc/trees/layer_tree_host_common_unittest.cc
+++ b/cc/trees/layer_tree_host_common_unittest.cc
@@ -8904,5 +8904,40 @@ TEST_F(LayerTreeHostCommonTest, CombineClipsUsingContentTarget) {
   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