Fix InterstitialPageImplTest to fail if frame is not focused correctly.

content/browser/frame_host/interstitial_page_impl_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 "content/browser/frame_host/interstitial_page_impl.h"
 
 #include <tuple>
 
 #include "base/macros.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 131 matching lines @@
     GURL url("http://interstitial");
     interstitial_.reset(new InterstitialPageImpl(
         web_contents, static_cast<RenderWidgetHostDelegate*>(web_contents),
         true, url, interstitial_delegate));
     interstitial_->Show();
     WaitForInterstitialAttach(web_contents);
 
     // Focus the interstitial frame
     FrameTree* frame_tree = static_cast<RenderViewHostDelegate*>(
                                 interstitial_.get())->GetFrameTree();
-    frame_tree->SetFocusedFrame(frame_tree->root(),
-                                frame_tree->GetMainFrame()->GetSiteInstance());
+    static_cast<RenderFrameHostDelegate*>(interstitial_.get())
+        ->SetFocusedFrame(frame_tree->root(),
+                          frame_tree->GetMainFrame()->GetSiteInstance());
 
     clipboard_message_watcher_ =
         new ClipboardMessageWatcher(interstitial_.get());
 
     // Wait until page loads completely.
     ASSERT_TRUE(WaitForRenderFrameReady(interstitial_->GetMainFrame()));
   }
 
   void TearDownInterstitialPage() {
     // Close the interstitial.
@@ skipping 142 matching lines @@
 
   PerformSelectAll();
 
   ASSERT_TRUE(GetSelection(&input_text));
   EXPECT_EQ("original body text", input_text);
 
   TearDownInterstitialPage();
 }
 
 }  // namespace content