Allow a main interstitial frame to act as an ExtensionMessagePort opener

content/browser/frame_host/render_frame_host_delegate.cc

 // Copyright 2013 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 <stddef.h>
 
 #include "base/callback.h"
 #include "base/strings/string16.h"
 #include "build/build_config.h"
 #include "content/browser/frame_host/render_frame_host_delegate.h"
@@ skipping 18 matching lines @@
     const base::string16& message,
     int32_t line_no,
     const base::string16& source_id) {
   return false;
 }
 
 WebContents* RenderFrameHostDelegate::GetAsWebContents() {
   return NULL;
 }
 
+InterstitialPage* RenderFrameHostDelegate::GetAsInterstitialPage() {
+  return nullptr;
+}
+
 void RenderFrameHostDelegate::RequestMediaAccessPermission(
     const MediaStreamRequest& request,
     const MediaResponseCallback& callback) {
   LOG(ERROR) << "RenderFrameHostDelegate::RequestMediaAccessPermission: "
              << "Not supported.";
   callback.Run(MediaStreamDevices(),
                MEDIA_DEVICE_NOT_SUPPORTED,
                scoped_ptr<MediaStreamUI>());
 }
 
@@ skipping 36 matching lines @@
 }
 
 #if defined(OS_WIN)
 gfx::NativeViewAccessible
     RenderFrameHostDelegate::GetParentNativeViewAccessible() {
   return NULL;
 }
 #endif  // defined(OS_WIN)
 
 }  // namespace content