Add optimization for CHROMIUM_subscribe_uniform extension.

content/common/gpu/gpu_channel.cc

Index: content/common/gpu/gpu_channel.cc
diff --git a/content/common/gpu/gpu_channel.cc b/content/common/gpu/gpu_channel.cc
index 7bf61344c8fb2029e179fd21b2a92e5a9219f7c6..b3e2fac0a6eedbbaa75ba8363adc874371dcb555 100644
--- a/content/common/gpu/gpu_channel.cc
+++ b/content/common/gpu/gpu_channel.cc
@@ -29,6 +29,7 @@
 #include "gpu/command_buffer/service/image_factory.h"
 #include "gpu/command_buffer/service/mailbox_manager_impl.h"
 #include "gpu/command_buffer/service/sync_point_manager.h"
+#include "gpu/command_buffer/service/valuebuffer_manager.h"
 #include "ipc/ipc_channel.h"
 #include "ipc/message_filter.h"
 #include "ui/gl/gl_context.h"
@@ -425,10 +426,14 @@ GpuChannel::GpuChannel(GpuChannelManager* gpu_channel_manager,
   const base::CommandLine* command_line =
       base::CommandLine::ForCurrentProcess();
   log_messages_ = command_line->HasSwitch(switches::kLogPluginMessages);
+
+  subscription_ref_set_ = new gpu::gles2::SubscriptionRefSet();
+  subscription_ref_set_->AddObserver(this);
 }
 
 GpuChannel::~GpuChannel() {
   STLDeleteElements(&deferred_messages_);
+  subscription_ref_set_->RemoveObserver(this);
   if (preempting_flag_.get())
     preempting_flag_->Reset();
 }
@@ -512,6 +517,16 @@ bool GpuChannel::Send(IPC::Message* message) {
   return channel_->Send(message);
 }
 
+void GpuChannel::OnAddSubscription(unsigned int target) {
+  gpu_channel_manager()->Send(
+      new GpuHostMsg_AddSubscription(client_id_, target));
+}
+
+void GpuChannel::OnRemoveSubscription(unsigned int target) {
+  gpu_channel_manager()->Send(
+      new GpuHostMsg_RemoveSubscription(client_id_, target));
+}
+
 void GpuChannel::RequeueMessage() {
   DCHECK(currently_processing_message_);
   deferred_messages_.push_front(
@@ -581,6 +596,7 @@ CreateCommandBufferResult GpuChannel::CreateViewCommandBuffer(
                                share_group,
                                window,
                                mailbox_manager_.get(),
+                               subscription_ref_set_.get(),
                                pending_valuebuffer_state_.get(),
                                gfx::Size(),
                                disallowed_features_,
@@ -740,6 +756,7 @@ void GpuChannel::OnCreateOffscreenCommandBuffer(
       share_group,
       gfx::GLSurfaceHandle(),
       mailbox_manager_.get(),
+      subscription_ref_set_.get(),
       pending_valuebuffer_state_.get(),
       size,
       disallowed_features_,