Fix copying from interstitial pages on OSX.

content/browser/renderer_host/render_widget_host_view_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_view_mac.h"
 
 #import <objc/runtime.h>
 #include <OpenGL/gl.h>
 #include <QuartzCore/QuartzCore.h>
 
@@ skipping 1349 matching lines @@
 
   return gfx::Range(
       request_range.start() - composition_range_.start(),
       request_range.end() - composition_range_.start());
 }
 
 WebContents* RenderWidgetHostViewMac::GetWebContents() {
   if (!render_widget_host_->IsRenderView())
     return NULL;
 
-  return WebContents::FromRenderViewHost(
-      RenderViewHost::From(render_widget_host_));
+  return WebContents::FromRenderFrameHost(
+      RenderViewHost::From(render_widget_host_)->GetMainFrame());
 }
 
 bool RenderWidgetHostViewMac::GetCachedFirstRectForCharacterRange(
     NSRange range,
     NSRect* rect,
     NSRange* actual_range) {
   DCHECK(rect);
   // This exists to make IMEs more responsive, see http://crbug.com/115920
   TRACE_EVENT0("browser",
                "RenderWidgetHostViewMac::GetFirstRectForCharacterRange");
@@ skipping 1989 matching lines @@
 
 // "-webkit-app-region: drag | no-drag" is implemented on Mac by excluding
 // regions that are not draggable. (See ControlRegionView in
 // native_app_window_cocoa.mm). This requires the render host view to be
 // draggable by default.
 - (BOOL)mouseDownCanMoveWindow {
   return YES;
 }
 
 @end