cc: Commit property trees to the compositor thread

cc/trees/layer_tree_host_unittest.cc

Index: cc/trees/layer_tree_host_unittest.cc
diff --git a/cc/trees/layer_tree_host_unittest.cc b/cc/trees/layer_tree_host_unittest.cc
index ff8c5e8e06d80cbe123437c413d93c81c93512f1..7843fb45ae98c400d9ce51ac8f14e5a319aaba70 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -3285,6 +3285,9 @@ class PushPropertiesCountingLayer : public Layer {
       needs_push_properties_ = true;
   }
 
+  // Something to make this layer push properties, but no other layer.
+  void MakePushProperties() { SetContentsOpaque(!contents_opaque()); }
+
   scoped_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl) override {
     return PushPropertiesCountingLayerImpl::Create(tree_impl, id());
   }
@@ -3344,18 +3347,24 @@ class LayerTreeHostTestLayersPushProperties : public LayerTreeHostTest {
   }
 
   void DidCommitAndDrawFrame() override {
-    ++num_commits_;
-
-    EXPECT_EQ(expected_push_properties_root_, root_->push_properties_count());
-    EXPECT_EQ(expected_push_properties_child_, child_->push_properties_count());
+    EXPECT_EQ(expected_push_properties_root_, root_->push_properties_count())
+        << "num_commits: " << num_commits_;
+    EXPECT_EQ(expected_push_properties_child_, child_->push_properties_count())
+        << "num_commits: " << num_commits_;
     EXPECT_EQ(expected_push_properties_grandchild_,
-              grandchild_->push_properties_count());
+              grandchild_->push_properties_count())
+        << "num_commits: " << num_commits_;
     EXPECT_EQ(expected_push_properties_child2_,
-              child2_->push_properties_count());
+              child2_->push_properties_count())
+        << "num_commits: " << num_commits_;
     EXPECT_EQ(expected_push_properties_other_root_,
-              other_root_->push_properties_count());
+              other_root_->push_properties_count())
+        << "num_commits: " << num_commits_;
     EXPECT_EQ(expected_push_properties_leaf_layer_,
-              leaf_always_pushing_layer_->push_properties_count());
+              leaf_always_pushing_layer_->push_properties_count())
+        << "num_commits: " << num_commits_;
+
+    ++num_commits_;
 
     // The scrollbar layer always needs to be pushed.
     if (root_->layer_tree_host()) {
@@ -3445,12 +3454,12 @@ class LayerTreeHostTestLayersPushProperties : public LayerTreeHostTest {
         // No layers need commit.
         break;
       case 12:
-        child_->SetPosition(gfx::Point(1, 1));

[enne (OOO), 2015/04/17 20:59:36]

This code used to adjust the offset of children which would cause a property
push.

This in practice will cause more push properties when any parent moves around.

Alternatively, maybe "offset from parent" is a draw property-style piece of data
that should be recomputed on the compositor thread?

[ajuma, 2015/04/17 22:53:11]

If these extra pushes turn out to be costly, perhaps another alternative would
be to have a finer-grained PushPropertyTreeProperties instead of pushing all the
properties? My hand-wavy guess is that this would turn out to be cheaper than
re-computing all the offsets on the compositor side (since pushing would mean
visiting some of the layers when offsets change and copying an offset at each
visited layer, but re-computing on the compositor side would involve visiting
all of the layers after every commit and doing some math that's more complex
that just copying an offset).

+        child_->MakePushProperties();
         // The modified layer needs commit
         ++expected_push_properties_child_;
         break;
       case 13:
-        child2_->SetPosition(gfx::Point(1, 1));
+        child2_->MakePushProperties();
         // The modified layer needs commit
         ++expected_push_properties_child2_;
         break;
@@ -3462,7 +3471,7 @@ class LayerTreeHostTestLayersPushProperties : public LayerTreeHostTest {
         ++expected_push_properties_grandchild_;
         break;
       case 15:
-        grandchild_->SetPosition(gfx::Point(1, 1));
+        grandchild_->MakePushProperties();
         // The modified layer needs commit
         ++expected_push_properties_grandchild_;
         break;