Delete background tab IOSurfaces on Mac.

content/browser/renderer_host/render_widget_host_view_gtk.cc

Index: content/browser/renderer_host/render_widget_host_view_gtk.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_gtk.cc b/content/browser/renderer_host/render_widget_host_view_gtk.cc
index 466d1d182951e2b164b3d299c629015b9cc496fd..15a007381aedb42bfcf0924521bde69bc67accd2 100644
--- a/content/browser/renderer_host/render_widget_host_view_gtk.cc
+++ b/content/browser/renderer_host/render_widget_host_view_gtk.cc
@@ -1011,6 +1011,13 @@ void RenderWidgetHostViewGtk::AcceleratedSurfacePostSubBuffer(
 void RenderWidgetHostViewGtk::AcceleratedSurfaceSuspend() {
 }
 
+bool RenderWidgetHostViewGtk::HasAcceleratedSurface(
+      const gfx::Size& desired_size) {
+  // TODO(jbates) Implement this so this view can use GetBackingStore for both
+  // software and GPU frames. Defaulting to false just makes GetBackingStore
+  // only useable for software frames.
+  return false;
+}
 
 void RenderWidgetHostViewGtk::SetBackground(const SkBitmap& background) {
   content::RenderWidgetHostViewBase::SetBackground(background);