Add optimization for CHROMIUM_subscribe_uniform extension.

content/common/gpu/gpu_channel.h

Index: content/common/gpu/gpu_channel.h
diff --git a/content/common/gpu/gpu_channel.h b/content/common/gpu/gpu_channel.h
index 6b707289cc55df3a924f66619667f332ceeb7966..0db58ef5a41cb56d90a1d539ca586fbd6b3cb7e8 100644
--- a/content/common/gpu/gpu_channel.h
+++ b/content/common/gpu/gpu_channel.h
@@ -19,6 +19,7 @@
 #include "content/common/gpu/gpu_memory_manager.h"
 #include "content/common/gpu/gpu_result_codes.h"
 #include "content/common/message_router.h"
+#include "gpu/command_buffer/service/valuebuffer_manager.h"
 #include "ipc/ipc_sync_channel.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/size.h"
@@ -37,6 +38,7 @@ class PreemptionFlag;
 union ValueState;
 class ValueStateMap;
 namespace gles2 {
+class SubscriptionRefSet;
 }
 }
 
@@ -52,7 +54,8 @@ class GpuWatchdog;
 
 // Encapsulates an IPC channel between the GPU process and one renderer
 // process. On the renderer side there's a corresponding GpuChannelHost.
-class GpuChannel : public IPC::Listener, public IPC::Sender {
+class GpuChannel : public IPC::Listener, public IPC::Sender,
+                   public gpu::gles2::SubscriptionRefSet::Observer {
  public:
   // Takes ownership of the renderer process handle.
   GpuChannel(GpuChannelManager* gpu_channel_manager,
@@ -99,6 +102,10 @@ class GpuChannel : public IPC::Listener, public IPC::Sender {
   // unscheduling conditions.
   void RequeueMessage();
 
+  // SubscriptionRefSet::Observer implementation
+  void OnAddSubscription(unsigned int target) override;
+  void OnRemoveSubscription(unsigned int target) override;
+
   // This is called when a command buffer transitions from the unscheduled
   // state to the scheduled state, which potentially means the channel
   // transitions from the unscheduled to the scheduled state. When this occurs
@@ -219,6 +226,8 @@ class GpuChannel : public IPC::Listener, public IPC::Sender {
 
   scoped_refptr<gpu::gles2::MailboxManager> mailbox_manager_;
 
+  scoped_refptr<gpu::gles2::SubscriptionRefSet> subscription_ref_set_;
+
   scoped_refptr<gpu::ValueStateMap> pending_valuebuffer_state_;
 
   typedef IDMap<GpuCommandBufferStub, IDMapOwnPointer> StubMap;