Fix copying from interstitial pages on OSX by going through the RenderWidgetHostDelegate.

content/browser/frame_host/interstitial_page_impl.h

Index: content/browser/frame_host/interstitial_page_impl.h
diff --git a/content/browser/frame_host/interstitial_page_impl.h b/content/browser/frame_host/interstitial_page_impl.h
index a509c1b69da64bd8d2552be04d458fbfc8b63093..697621d0a58521785b9a3eccbd9887312a79019f 100644
--- a/content/browser/frame_host/interstitial_page_impl.h
+++ b/content/browser/frame_host/interstitial_page_impl.h
@@ -56,6 +56,16 @@ class CONTENT_EXPORT InterstitialPageImpl
                        InterstitialPageDelegate* delegate);
   ~InterstitialPageImpl() override;
 
+  // RenderWidgetHostDelegate implementation:
+  void Undo() override;
+  void Redo() override;
+  void Cut() override;
+  void Copy() override;
+  void CopyToFindPboard() override;
+  void Paste() override;
+  void PasteAndMatchStyle() override;
+  void SelectAll() override;
+
   // InterstitialPage implementation:
   void Show() override;
   void Hide() override;