Make PageScaleFactor work for oopif subframes.

content/browser/frame_host/render_frame_host_delegate.h

Index: content/browser/frame_host/render_frame_host_delegate.h
diff --git a/content/browser/frame_host/render_frame_host_delegate.h b/content/browser/frame_host/render_frame_host_delegate.h
index 4f3178036cda45d6dee1f0b9e6f4d0bbd2672ad9..0e6ae2c90d38b21f852090e0352ea34099e79941 100644
--- a/content/browser/frame_host/render_frame_host_delegate.h
+++ b/content/browser/frame_host/render_frame_host_delegate.h
@@ -269,6 +269,9 @@ class CONTENT_EXPORT RenderFrameHostDelegate {
                                  const gfx::Rect& initial_rect,
                                  bool user_gesture) {}
 
+  // Distribute page scale factor to all subframes.
+  virtual void SetPageScaleFactorForSubframes(double page_scale_factor) {}
+
  protected:
   virtual ~RenderFrameHostDelegate() {}
 };