Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

content/shell/renderer/layout_test/blink_test_runner.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_SHELL_RENDERER_LAYOUT_TEST_BLINK_TEST_RUNNER_H_
 #define CONTENT_SHELL_RENDERER_LAYOUT_TEST_BLINK_TEST_RUNNER_H_
 
 #include <deque>
 #include <memory>
 #include <vector>
@@ skipping 161 matching lines @@
   void OnSessionHistory(
       const std::vector<int>& routing_ids,
       const std::vector<std::vector<PageState> >& session_histories,
       const std::vector<unsigned>& current_entry_indexes);
   void OnReset();
   void OnTestFinishedInSecondaryRenderer();
   void OnTryLeakDetection();
   void OnReplyBluetoothManualChooserEvents(
       const std::vector<std::string>& events);
 
+  // RenderViewObserver implementation.
+  void OnDestruct() override;
+
   // After finishing the test, retrieves the audio, text, and pixel dumps from
   // the TestRunner library and sends them to the browser process.
   void CaptureDump();
   void OnLayoutDumpCompleted(std::string completed_layout_dump);
   void CaptureDumpContinued();
   void OnPixelsDumpCompleted(const SkBitmap& snapshot);
   void CaptureDumpComplete();
   std::string DumpHistoryForWindow(blink::WebView* web_view);
 
   mojom::LayoutTestBluetoothFakeAdapterSetter&
@@ skipping 16 matching lines @@
   bool focus_on_next_commit_;
 
   std::unique_ptr<LeakDetector> leak_detector_;
 
   DISALLOW_COPY_AND_ASSIGN(BlinkTestRunner);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_SHELL_RENDERER_LAYOUT_TEST_BLINK_TEST_RUNNER_H_