cc: add layer usage hint to texture layer

cc/texture_layer.cc

Index: cc/texture_layer.cc
diff --git a/cc/texture_layer.cc b/cc/texture_layer.cc
index ffb22ac0ed9dee71993e9b3afe0befd5a93650e5..05d757a6a7d929db7ceb14ada493137ff7ffad71 100644
--- a/cc/texture_layer.cc
+++ b/cc/texture_layer.cc
@@ -26,15 +26,15 @@ static void PostCallbackToMainThread(
       base::Bind(&RunCallbackOnMainThread, callback, sync_point));
 }
 
-scoped_refptr<TextureLayer> TextureLayer::Create(TextureLayerClient* client) {
-  return scoped_refptr<TextureLayer>(new TextureLayer(client, false));
+scoped_refptr<TextureLayer> TextureLayer::Create(TextureLayerClient* client, bool single_buffer) {
+  return scoped_refptr<TextureLayer>(new TextureLayer(client, false, single_buffer));
 }
 
 scoped_refptr<TextureLayer> TextureLayer::CreateForMailbox() {
-  return scoped_refptr<TextureLayer>(new TextureLayer(NULL, true));
+  return scoped_refptr<TextureLayer>(new TextureLayer(NULL, true, false));
 }
 
-TextureLayer::TextureLayer(TextureLayerClient* client, bool uses_mailbox)
+TextureLayer::TextureLayer(TextureLayerClient* client, bool uses_mailbox, bool single_buffer)
     : Layer(),
       client_(client),
       uses_mailbox_(uses_mailbox),
@@ -46,7 +46,8 @@ TextureLayer::TextureLayer(TextureLayerClient* client, bool uses_mailbox)
       context_lost_(false),
       texture_id_(0),
       content_committed_(false),
-      own_mailbox_(false) {
+      own_mailbox_(false),
+      single_buffer_(single_buffer) {
   vertex_opacity_[0] = 1.0f;
   vertex_opacity_[1] = 1.0f;
   vertex_opacity_[2] = 1.0f;
@@ -192,9 +193,11 @@ void TextureLayer::PushPropertiesTo(LayerImpl* layer) {
 
 bool TextureLayer::BlocksPendingCommit() const {
   // Double-buffered texture layers need to be blocked until they can be made
-  // triple-buffered.  Single-buffered layers already prevent draws, so
-  // can block too for simplicity.
-  return DrawsContent();
+  // triple-buffered. Single-buffered layers already prevent draws.
+  if (single_buffer_)
+    return false;
+  else
+    return DrawsContent();
 }
 
 bool TextureLayer::CanClipSelf() const {