Setup LayerTree class, refactor 2 functions from LayerTreeHost to it.

cc/trees/tree_synchronizer_unittest.cc

Index: cc/trees/tree_synchronizer_unittest.cc
diff --git a/cc/trees/tree_synchronizer_unittest.cc b/cc/trees/tree_synchronizer_unittest.cc
index 81bfec180781f79763624d58a8596458b34f2c3a..bda85b7986543a2a069b8fed8431d5ebf1c032fc 100644
--- a/cc/trees/tree_synchronizer_unittest.cc
+++ b/cc/trees/tree_synchronizer_unittest.cc
@@ -217,8 +217,8 @@ TEST_F(TreeSynchronizerTest, SyncSimpleTreeReusingLayers) {
                           host_->active_tree());
 
   // We have to push properties to pick up the destruction list pointer.
-  TreeSynchronizer::PushLayerProperties(layer_tree_root->layer_tree_host(),
-                                        host_->active_tree());
+  TreeSynchronizer::PushLayerProperties(
+      layer_tree_root->layer_tree_host()->GetLayerTree(), host_->active_tree());
 
   // Add a new layer to the Layer side
   layer_tree_root->children()[0]->AddChild(
@@ -266,8 +266,8 @@ TEST_F(TreeSynchronizerTest, SyncSimpleTreeAndTrackStackingOrderChange) {
                           host_->active_tree());
 
   // We have to push properties to pick up the destruction list pointer.
-  TreeSynchronizer::PushLayerProperties(layer_tree_root->layer_tree_host(),
-                                        host_->active_tree());
+  TreeSynchronizer::PushLayerProperties(
+      layer_tree_root->layer_tree_host()->GetLayerTree(), host_->active_tree());
 
   host_->active_tree()->ResetAllChangeTracking();
 
@@ -280,8 +280,8 @@ TEST_F(TreeSynchronizerTest, SyncSimpleTreeAndTrackStackingOrderChange) {
   ExpectTreesAreIdentical(layer_tree_root.get(), layer_impl_tree_root,
                           host_->active_tree());
 
-  TreeSynchronizer::PushLayerProperties(layer_tree_root->layer_tree_host(),
-                                        host_->active_tree());
+  TreeSynchronizer::PushLayerProperties(
+      layer_tree_root->layer_tree_host()->GetLayerTree(), host_->active_tree());
 
   // Check that the impl thread properly tracked the change.
   EXPECT_FALSE(layer_impl_tree_root->LayerPropertyChanged());
@@ -316,8 +316,8 @@ TEST_F(TreeSynchronizerTest, SyncSimpleTreeAndProperties) {
   ExpectTreesAreIdentical(layer_tree_root.get(), layer_impl_tree_root,
                           host_->active_tree());
 
-  TreeSynchronizer::PushLayerProperties(layer_tree_root->layer_tree_host(),
-                                        host_->active_tree());
+  TreeSynchronizer::PushLayerProperties(
+      layer_tree_root->layer_tree_host()->GetLayerTree(), host_->active_tree());
 
   // Check that the property values we set on the Layer tree are reflected in
   // the LayerImpl tree.
@@ -366,8 +366,8 @@ TEST_F(TreeSynchronizerTest, ReuseLayerImplsAfterStructuralChange) {
                           host_->active_tree());
 
   // We have to push properties to pick up the destruction list pointer.
-  TreeSynchronizer::PushLayerProperties(layer_tree_root->layer_tree_host(),
-                                        host_->active_tree());
+  TreeSynchronizer::PushLayerProperties(
+      layer_tree_root->layer_tree_host()->GetLayerTree(), host_->active_tree());
 
   // Now restructure the tree to look like this:
   // root --- D ---+--- A
@@ -422,8 +422,9 @@ TEST_F(TreeSynchronizerTest, SyncSimpleTreeThenDestroy) {
                           host_->active_tree());
 
   // We have to push properties to pick up the destruction list pointer.
-  TreeSynchronizer::PushLayerProperties(old_layer_tree_root->layer_tree_host(),
-                                        host_->active_tree());
+  TreeSynchronizer::PushLayerProperties(
+      old_layer_tree_root->layer_tree_host()->GetLayerTree(),
+      host_->active_tree());
 
   // Remove all children on the Layer side.
   old_layer_tree_root->RemoveAllChildren();