Allow WebExternalTextureLayers to receive a bitmap along with a mailbox

cc/trees/layer_tree_host.h

Index: cc/trees/layer_tree_host.h
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index 2c733fc7ec82a2d48d869c953595a1bdee3f97c7..9019a5dfe1c7c4b66596b606fbe2961dadcda438 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -259,6 +259,8 @@ class CC_EXPORT LayerTreeHost : NON_EXPORTED_BASE(public RateLimiterClient) {
       bool update_total_num_cc_layers_can_use_lcd_text,
       bool update_total_num_cc_layers_will_use_lcd_text);
 
+  bool UsingSoftwareRenderer();
+
  protected:
   LayerTreeHost(LayerTreeHostClient* client, const LayerTreeSettings& settings);
   bool Initialize(scoped_ptr<Thread> impl_thread);
@@ -365,6 +367,8 @@ class CC_EXPORT LayerTreeHost : NON_EXPORTED_BASE(public RateLimiterClient) {
   };
   LCDTextMetrics lcd_text_metrics_;
 
+  bool using_software_renderer_;
+
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };