Add optimization for CHROMIUM_subscribe_uniform extension.

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 454bb17ffbbd957e0e77150b51ac82c0f9b7048f..3207028f08a69178f77172c2f5bc70027beb725e 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -61,6 +61,11 @@ namespace gfx {
 class Range;
 }
 
+namespace gpu {
+union ValueState;
+class ValueStateMap;
+}
+
 namespace ui {
 class KeyEvent;
 }
@@ -473,6 +478,10 @@ class CONTENT_EXPORT RenderWidgetHostImpl
 
   InputRouter* input_router() { return input_router_.get(); }
 
+  // Handlers for subscription target changes to update subscription_set_
+  void OnAddSubscription(unsigned int target);
+  void OnRemoveSubscription(unsigned int target);
+
   // Get the BrowserAccessibilityManager for the root of the frame tree,
   BrowserAccessibilityManager* GetRootBrowserAccessibilityManager();
 
@@ -697,6 +706,8 @@ class CONTENT_EXPORT RenderWidgetHostImpl
       int snapshot_id,
       scoped_refptr<base::RefCountedBytes> png_data);
 
+  void SendUpdateValueState(unsigned int target, const gpu::ValueState& state);
+
   // Our delegate, which wants to know mainly about keyboard events.
   // It will remain non-NULL until DetachDelegate() is called.
   RenderWidgetHostDelegate* delegate_;
@@ -849,6 +860,17 @@ class CONTENT_EXPORT RenderWidgetHostImpl
       base::Callback<void(const unsigned char*, size_t)> > PendingSnapshotMap;
   PendingSnapshotMap pending_browser_snapshots_;
 
+  // This is a set of all subscription targets valuebuffers in the GPU process
+  // are currently subscribed too. Used to prevent sending unnecessary
+  // ValueState updates.
+  typedef base::hash_set<unsigned int> SubscriptionSet;
+  SubscriptionSet subscription_set_;
+
+  // Maintains ValueStates which are not currently subscribed too so we can
+  // pass them to the GpuService if a Valuebuffer ever subscribes to the
+  // respective subscription target
+  scoped_refptr<gpu::ValueStateMap> pending_valuebuffer_state_;
+
   base::WeakPtrFactory<RenderWidgetHostImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostImpl);