Perform glReadPixels with PBOs in the gpu, if PBOs are available.

cc/resources/sync_point_helper.h

Index: cc/resources/sync_point_helper.h
diff --git a/cc/resources/sync_point_helper.h b/cc/resources/sync_point_helper.h
index c342069bc7e2b70f4e6a676c2f7192d610f2f29e..905b12e7d1e7227208a550947bda000c52b40442 100644
--- a/cc/resources/sync_point_helper.h
+++ b/cc/resources/sync_point_helper.h
@@ -7,8 +7,7 @@
 
 #include "base/callback.h"
 #include "cc/base/cc_export.h"
-
-namespace WebKit { class WebGraphicsContext3D; }
+#include "third_party/WebKit/public/platform/WebGraphicsContext3D.h"
 
 namespace cc {
 
@@ -25,6 +24,11 @@ class CC_EXPORT SyncPointHelper {
       unsigned sync_point,
       const base::Closure& closure);
 
+  static void SignalQuery(

[danakj, 2013/06/17 18:36:48]

nit: add a comment here to describe the function?

[hubbe, 2013/06/17 19:47:19]

Done.

+      WebKit::WebGraphicsContext3D* context3d,
+      WebKit::WebGLId query,
+      const base::Closure& closure);
+
  private:
   SyncPointHelper();