Delete background tab IOSurfaces on Mac.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 8dd248c5533ef786b63425066235d3b8e6ecbbf9..024cbd965b8e5a6c61f1b8078468ce8939e3019c 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -641,6 +641,14 @@ void RenderWidgetHostViewAura::AcceleratedSurfacePostSubBuffer(
 void RenderWidgetHostViewAura::AcceleratedSurfaceSuspend() {
 }
 
+bool RenderWidgetHostViewAura::HasAcceleratedSurface(
+      const gfx::Size& desired_size) {
+  // Aura doesn't use GetBackingStore for accelerated pages, so it doesn't
+  // matter what is returned here as GetBackingStore is the only caller of this
+  // method. TODO(jbates) implement this if other Aura code needs it.
+  return false;
+}
+
 void RenderWidgetHostViewAura::AcceleratedSurfaceNew(
       int32 width,
       int32 height,