Simplify rate limiting since it's main thread shared context only

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index 634044a8330fddd5bb6a35e70e49f1052524bb3e..bea8b07d386b5ab5c95626fd4ae3f2047ba846eb 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -648,4 +648,10 @@ RenderWidgetCompositor::OffscreenContextProvider() {
   return RenderThreadImpl::current()->OffscreenCompositorContextProvider();
 }
 
+void RenderWidgetCompositor::RateLimitSharedMainThreadContext() {
+  cc::ContextProvider* provider =
+      RenderThreadImpl::current()->SharedMainThreadContextProvider().get();
+  provider->Context3d()->rateLimitOffscreenContextCHROMIUM();
+}
+
 }  // namespace content