Extend the ToRenderFrameHost magic to FrameTreeNode* and Shell*

content/browser/media/midi_browsertest.cc

 // Copyright 2016 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 "content/public/test/browser_test_utils.h"
 #include "content/public/test/content_browser_test.h"
 #include "content/public/test/content_browser_test_utils.h"
 #include "content/shell/browser/shell.h"
 
 namespace content {
 
 class MidiBrowserTest : public ContentBrowserTest {
  public:
   MidiBrowserTest() {}
   ~MidiBrowserTest() override {}
 };
 
 IN_PROC_BROWSER_TEST_F(MidiBrowserTest, RequestMIDIAccess) {
   bool result;
   NavigateToURL(shell(), GURL("about:blank"));
   ASSERT_TRUE(ExecuteScriptAndExtractBool(
-      shell()->web_contents(),
+      shell(),
       "navigator.requestMIDIAccess()"
       "  .then("
       "    _ => domAutomationController.send(true),"
       "    _ => domAutomationController.send(false));",
       &result));
   // We cannot check result since it relies on the availabity of system
   // level MIDI on the test runner.
 }
 
 IN_PROC_BROWSER_TEST_F(MidiBrowserTest, SubscribeAll) {
   bool result;
   NavigateToURL(shell(), GURL("about:blank"));
   ASSERT_TRUE(ExecuteScriptAndExtractBool(
-      shell()->web_contents(),
+      shell(),
       "navigator.requestMIDIAccess()"
       "  .then("
       "    e => { e.inputs.forEach(i => i.onmidimessage = console.log);"
       "             domAutomationController.send(true) },"
       "    _ => domAutomationController.send(false));",
       &result));
   // We cannot check result since it relies on the availabity of system
   // level MIDI on the test runner.
 }
 
 }  // namespace content