Implement client side PBOs for glReadPixel

content/browser/renderer_host/image_transport_factory.cc

Index: content/browser/renderer_host/image_transport_factory.cc
diff --git a/content/browser/renderer_host/image_transport_factory.cc b/content/browser/renderer_host/image_transport_factory.cc
index be01420b702cfe4b776474e9fbd9c66e5d399f77..1d16958b5ff30cb022e8448a99493cd1e9970339 100644
--- a/content/browser/renderer_host/image_transport_factory.cc
+++ b/content/browser/renderer_host/image_transport_factory.cc
@@ -466,13 +466,7 @@ class GpuProcessTransportFactory
       CreateSharedContextLazy();
       WebKit::WebGraphicsContext3D* context_for_main_thread =
           shared_contexts_main_thread_->Context3d();
-      WebKit::WebGraphicsContext3D* context_for_thread =
-          CreateOffscreenContext();
-      if (!context_for_thread)
-        return NULL;
-
-      gl_helper_.reset(new GLHelper(context_for_main_thread,
-                                    context_for_thread));
+      gl_helper_.reset(new GLHelper(context_for_main_thread));
     }
     return gl_helper_.get();
   }