Use fast path of mailbox generation in RGVAF::CreateTextures.

content/renderer/media/renderer_gpu_video_accelerator_factories.cc

Index: content/renderer/media/renderer_gpu_video_accelerator_factories.cc
diff --git a/content/renderer/media/renderer_gpu_video_accelerator_factories.cc b/content/renderer/media/renderer_gpu_video_accelerator_factories.cc
index f586497f484a8b83135f7ec82c213096ddf76aac..c373d882792b1b961e495ea9ce2d41bddd6da651 100644
--- a/content/renderer/media/renderer_gpu_video_accelerator_factories.cc
+++ b/content/renderer/media/renderer_gpu_video_accelerator_factories.cc
@@ -223,7 +223,9 @@ void RendererGpuVideoAcceleratorFactories::AsyncCreateTextures(
                         GL_UNSIGNED_BYTE,
                         NULL);
     }
-    gles2->GenMailboxCHROMIUM(created_texture_mailboxes_[i].name);
+    // GLES2Implementation doesn't currently have the fast path of mailbox
+    // generation, but WebGraphicsContext3DCommandBufferImpl does.
+    context_->genMailboxCHROMIUM(created_texture_mailboxes_[i].name);
     gles2->ProduceTextureCHROMIUM(texture_target,
                                   created_texture_mailboxes_[i].name);
   }