Add optimization for CHROMIUM_subscribe_uniform extension.

content/browser/gpu/gpu_process_host.h

Index: content/browser/gpu/gpu_process_host.h
diff --git a/content/browser/gpu/gpu_process_host.h b/content/browser/gpu/gpu_process_host.h
index 145cdcccc2b9c16bfcb637e445f0cc141b1b7360..20da8cee9a6b953811af2f71e41597cca6d68eaf 100644
--- a/content/browser/gpu/gpu_process_host.h
+++ b/content/browser/gpu/gpu_process_host.h
@@ -23,6 +23,7 @@
 #include "content/public/browser/browser_child_process_host_delegate.h"
 #include "content/public/browser/gpu_data_manager.h"
 #include "gpu/command_buffer/common/constants.h"
+#include "gpu/command_buffer/common/value_state.h"
 #include "gpu/config/gpu_info.h"
 #include "ipc/ipc_sender.h"
 #include "ipc/message_filter.h"
@@ -86,6 +87,9 @@ class GpuProcessHost : public BrowserChildProcessHostDelegate,
                                       CauseForGpuLaunch cause,
                                       IPC::Message* message);
 
+  CONTENT_EXPORT static void SendUpdateValueStateOnIOThread(
+      int client_id, unsigned int target, const gpu::ValueState& state);
+
   CONTENT_EXPORT static void RegisterGpuMainThreadFactory(
       GpuMainThreadFactoryFunction create);
 
@@ -142,6 +146,10 @@ class GpuProcessHost : public BrowserChildProcessHostDelegate,
   void EndFrameSubscription(int surface_id);
   void LoadedShader(const std::string& key, const std::string& data);
 
+  void SendUpdateValueState(int client_id,
+                            unsigned int target,
+                            const gpu::ValueState& state);
+
  private:
   static bool ValidateHost(GpuProcessHost* host);
 
@@ -179,6 +187,8 @@ class GpuProcessHost : public BrowserChildProcessHostDelegate,
   void OnDestroyChannel(int32 client_id);
   void OnCacheShader(int32 client_id, const std::string& key,
                      const std::string& shader);
+  void OnAddSubscription(unsigned int target);
+  void OnRemoveSubscription(unsigned int target);
 
   bool LaunchGpuProcess(const std::string& channel_id);
 
@@ -276,6 +286,12 @@ class GpuProcessHost : public BrowserChildProcessHostDelegate,
       SurfaceRefMap;
   SurfaceRefMap surface_refs_;
 
+  // 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_;
+
   DISALLOW_COPY_AND_ASSIGN(GpuProcessHost);
 };