Use WebViewHelper::LocalMainFrame where possible.

third_party/WebKit/Source/core/frame/FrameTestHelpers.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 248 matching lines @@
   WebViewBase* InitializeRemote(TestWebRemoteFrameClient* = nullptr,
                                 RefPtr<SecurityOrigin> = nullptr,
                                 TestWebViewClient* = nullptr);
 
   void Resize(WebSize);
 
   void Reset();
 
   WebViewBase* WebView() const { return web_view_; }
 
-  WebLocalFrameBase* LocalMainFrame();
-  WebRemoteFrameBase* RemoteMainFrame();
+  WebLocalFrameBase* LocalMainFrame() const;
+  WebRemoteFrameBase* RemoteMainFrame() const;
 
  private:
   void InitializeWebView(TestWebViewClient*);
 
   WebViewBase* web_view_;
   UseMockScrollbarSettings mock_scrollbar_settings_;
   // Non-null if the WebViewHelper owns the TestWebViewClient.
   std::unique_ptr<TestWebViewClient> owned_test_web_view_client_;
   TestWebViewClient* test_web_view_client_;
 };
@@ skipping 75 matching lines @@
 
   // This is null from when the client is created until it is initialized with
   // Bind().
   WebRemoteFrame* frame_ = nullptr;
 };
 
 }  // namespace FrameTestHelpers
 }  // namespace blink
 
 #endif  // FrameTestHelpers_h