Add some missing virtual destructors to base classes.

content/renderer/devtools/v8_sampling_profiler.h

 // Copyright 2014 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_RENDERER_DEVTOOLS_V8_SAMPLING_PROFILER_H_
 #define CONTENT_RENDERER_DEVTOOLS_V8_SAMPLING_PROFILER_H_
 
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/trace_event/trace_event_impl.h"
 #include "content/common/content_export.h"
 
 namespace content {
 
 class Sampler;
 class V8SamplingThread;
 
 // The class monitors enablement of V8 CPU profiler and
 // spawns a sampling thread when needed.
 class CONTENT_EXPORT V8SamplingProfiler final
     : public base::trace_event::TraceLog::EnabledStateObserver {
  public:
   explicit V8SamplingProfiler(bool underTest = false);
-  ~V8SamplingProfiler();
+  ~V8SamplingProfiler() override;
 
   // Implementation of TraceLog::EnabledStateObserver
   void OnTraceLogEnabled() override;
   void OnTraceLogDisabled() override;
 
   void EnableSamplingEventForTesting(int code_added_events, int sample_events);
   void WaitSamplingEventForTesting();
 
  private:
   void StartSamplingThread();
   void StopSamplingThread();
 
   scoped_ptr<base::WaitableEvent> waitable_event_for_testing_;
   scoped_ptr<V8SamplingThread> sampling_thread_;
   scoped_ptr<Sampler> render_thread_sampler_;
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(V8SamplingProfiler);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_DEVTOOLS_V8_SAMPLING_PROFILER_H_