Use WebViewHelper::LocalMainFrame where possible.

third_party/WebKit/Source/web/tests/DocumentLoaderTest.cpp

 // Copyright 2015 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 "core/loader/DocumentLoader.h"
 
 #include <queue>
 #include "core/frame/FrameTestHelpers.h"
 #include "core/frame/WebLocalFrameBase.h"
 #include "core/page/Page.h"
@@ skipping 17 matching lines @@
         URLTestHelpers::ToKURL("https://example.com/foo.html"),
         testing::WebTestDataPath("foo.html"));
   }
 
   void TearDown() override {
     Platform::Current()
         ->GetURLLoaderMockFactory()
         ->UnregisterAllURLsAndClearMemoryCache();
   }
 
-  WebLocalFrameBase* MainFrame() {
-    return web_view_helper_.WebView()->MainFrameImpl();
-  }
+  WebLocalFrameBase* MainFrame() { return web_view_helper_.LocalMainFrame(); }
 
   FrameTestHelpers::WebViewHelper web_view_helper_;
 };
 
 TEST_F(DocumentLoaderTest, SingleChunk) {
   class TestDelegate : public WebURLLoaderTestDelegate {
    public:
     void DidReceiveData(WebURLLoaderClient* original_client,
                         const char* data,
                         int data_length) override {
@@ skipping 138 matching lines @@
 TEST_F(DocumentLoaderTest, isCommittedButEmpty) {
   WebViewBase* web_view_impl =
       web_view_helper_.InitializeAndLoad("about:blank");
   EXPECT_TRUE(ToLocalFrame(web_view_impl->GetPage()->MainFrame())
                   ->Loader()
                   .GetDocumentLoader()
                   ->IsCommittedButEmpty());
 }
 
 }  // namespace blink