Remove cancelMediaDevicesRequest dead code.

components/test_runner/mock_web_user_media_client.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 COMPONENTS_TEST_RUNNER_MOCK_WEB_USER_MEDIA_CLIENT_H_
 #define COMPONENTS_TEST_RUNNER_MOCK_WEB_USER_MEDIA_CLIENT_H_
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "third_party/WebKit/public/web/WebMediaDeviceChangeObserver.h"
 #include "third_party/WebKit/public/web/WebUserMediaClient.h"
 
 namespace test_runner {
 
 class WebTestDelegate;
 
 class MockWebUserMediaClient : public blink::WebUserMediaClient {
  public:
   explicit MockWebUserMediaClient(WebTestDelegate* delegate);
   ~MockWebUserMediaClient() override;
 
   void requestUserMedia(const blink::WebUserMediaRequest&) override;
   void cancelUserMediaRequest(const blink::WebUserMediaRequest&) override;
   void requestMediaDevices(const blink::WebMediaDevicesRequest&) override;
-  void cancelMediaDevicesRequest(const blink::WebMediaDevicesRequest&) override;
   void requestSources(const blink::WebMediaStreamTrackSourcesRequest&) override;
   void setMediaDeviceChangeObserver(
       const blink::WebMediaDeviceChangeObserver&) override;
 
  private:
   WebTestDelegate* delegate_;
   blink::WebMediaDeviceChangeObserver media_device_change_observer_;
   bool should_enumerate_extra_device_;
 
   base::WeakPtrFactory<MockWebUserMediaClient> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MockWebUserMediaClient);
 };
 
 }  // namespace test_runner
 
 #endif  // COMPONENTS_TEST_RUNNER_MOCK_WEB_USER_MEDIA_CLIENT_H_