Extend the ToRenderFrameHost magic to FrameTreeNode* and Shell*

content/browser/renderer_host/input/composited_scrolling_browsertest.cc

 // 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 <utility>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/macros.h"
 #include "base/run_loop.h"
@@ skipping 84 matching lines @@
     // otherwise the injection of the synthetic gestures may get
     // dropped because of MainThread/Impl thread sync of touch event
     // regions.
     frame_watcher->WaitFrames(1);
   }
 
   // ContentBrowserTest:
   int ExecuteScriptAndExtractInt(const std::string& script) {
     int value = 0;
     EXPECT_TRUE(content::ExecuteScriptAndExtractInt(
-        shell()->web_contents(),
-        "domAutomationController.send(" + script + ")",
-        &value));
+        shell(), "domAutomationController.send(" + script + ")", &value));
     return value;
   }
 
   int GetScrollTop() {
     return ExecuteScriptAndExtractInt(
         "document.getElementById(\"scroller\").scrollTop");
   }
 
   // Generate touch events for a synthetic scroll from |point| for |distance|.
   // Returns the distance scrolled.
@@ skipping 44 matching lines @@
                        MAYBE_Scroll3DTransformedScroller) {
   LoadURL();
   int scrollDistance =
       DoTouchScroll(gfx::Point(50, 150), gfx::Vector2d(0, 100));
   // The scroll distance is increased due to the rotation of the scroller.
   EXPECT_EQ(std::floor(100 / std::cos(cc::MathUtil::Deg2Rad(30.f))) - 1,
             scrollDistance);
 }
 
 }  // namespace content