Use WebViewHelper::LocalMainFrame where possible.

third_party/WebKit/Source/web/tests/CompositorWorkerTest.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 <gtest/gtest.h>
 #include <memory>
 #include "core/exported/WebViewBase.h"
 #include "core/frame/FrameTestHelpers.h"
 #include "core/frame/LocalFrameView.h"
 #include "core/frame/WebLocalFrameBase.h"
@@ skipping 73 matching lines @@
     PaintLayerCompositor* compositor =
         GetFrame()->ContentLayoutItem().Compositor();
     DCHECK(compositor);
     DCHECK(compositor->ScrollLayer());
 
     WebLayer* web_scroll_layer = compositor->ScrollLayer()->PlatformLayer();
     return web_scroll_layer;
   }
 
   WebViewBase* GetWebView() const { return helper_.WebView(); }
-  LocalFrame* GetFrame() const {
-    return helper_.WebView()->MainFrameImpl()->GetFrame();
-  }
+  LocalFrame* GetFrame() const { return helper_.LocalMainFrame()->GetFrame(); }
 
  protected:
   String base_url_;
 
  private:
   static void ConfigureSettings(WebSettings* settings) {
     settings->SetAcceleratedCompositingEnabled(true);
     settings->SetPreferCompositingToLCDTextEnabled(true);
   }
 
@@ skipping 264 matching lines @@
 
     const String& opacity_value =
         document->domWindow()
             ->getComputedStyle(proxied_element, String())
             ->GetPropertyValueInternal(CSSPropertyOpacity);
     EXPECT_EQ("0.8", opacity_value);
   }
 }
 
 }  // namespace blink