Add optimization for CHROMIUM_subscribe_uniform extension.

content/browser/renderer_host/render_widget_host_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 
 #include <math.h>
 #include <set>
 #include <utility>
 
@@ skipping 886 matching lines @@
     return;
 
   if (touch_emulator_ && touch_emulator_->HandleMouseEvent(mouse_event))
     return;
 
   input_router_->SendMouseEvent(MouseEventWithLatencyInfo(mouse_event,
                                                           latency_info));
 
   // Pass mouse state to gpu service if the subscribe uniform
   // extension is enabled.
-  // TODO(orglofch): Only pass mouse information if one of the GL Contexts
-  // is subscribed to GL_MOUSE_POSITION_CHROMIUM
   if (subscribe_uniform_enabled_) {
     gpu::ValueState state;
     state.int_value[0] = mouse_event.x;
     state.int_value[1] = mouse_event.y;
-    GpuProcessHost::SendOnIO(
-        GpuProcessHost::GPU_PROCESS_KIND_SANDBOXED,
-        CAUSE_FOR_GPU_LAUNCH_NO_LAUNCH,
-        new GpuMsg_UpdateValueState(
-            process_->GetID(), GL_MOUSE_POSITION_CHROMIUM, state));
+    GpuProcessHost::SendUpdateValueStateOnIOThread(
+          process_->GetID(), GL_MOUSE_POSITION_CHROMIUM, state);

[piman, 2014/12/05 21:04:36]

I was hoping we could filter here, on the UI thread. Otherwise we'll still post
tasks when no-one is subscribed (common case), that seems wasteful.

[orglofch, 2014/12/06 21:49:04]

Ah I had thought the main concern was IPC overhead. Done.

   }
 }
 
 void RenderWidgetHostImpl::OnPointerEventActivate() {
 }
 
 void RenderWidgetHostImpl::ForwardWheelEvent(
     const WebMouseWheelEvent& wheel_event) {
   ForwardWheelEventWithLatencyInfo(wheel_event, ui::LatencyInfo());
 }
@@ skipping 1501 matching lines @@
 }
 #endif
 
 SkColorType RenderWidgetHostImpl::PreferredReadbackFormat() {
   if (view_)
     return view_->PreferredReadbackFormat();
   return kN32_SkColorType;
 }
 
 }  // namespace content