Remove cancelMediaDevicesRequest dead code.

components/test_runner/mock_web_user_media_client.cc

 // 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.
 
 #include "components/test_runner/mock_web_user_media_client.h"
 
 #include <stddef.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 133 matching lines @@
 
   delegate_->PostTask(
       base::Bind(&WebMediaDevicesRequest::requestSucceeded,
                  base::Owned(new WebMediaDevicesRequest(request)), devices));
 
   should_enumerate_extra_device_ = !should_enumerate_extra_device_;
   if (!media_device_change_observer_.isNull())
     media_device_change_observer_.didChangeMediaDevices();
 }
 
-void MockWebUserMediaClient::cancelMediaDevicesRequest(
-    const WebMediaDevicesRequest&) {
-}
-
 void MockWebUserMediaClient::requestSources(
     const blink::WebMediaStreamTrackSourcesRequest& request) {
   struct {
     const char* id;
     WebSourceInfo::SourceKind kind;
     const char* label;
     WebSourceInfo::VideoFacingMode facing;
   } test_sources[] = {
     {
       "device1",
@@ skipping 21 matching lines @@
       &WebMediaStreamTrackSourcesRequest::requestSucceeded,
       base::Owned(new WebMediaStreamTrackSourcesRequest(request)), sources));
 }
 
 void MockWebUserMediaClient::setMediaDeviceChangeObserver(
     const blink::WebMediaDeviceChangeObserver& observer) {
   media_device_change_observer_ = observer;
 }
 
 }  // namespace test_runner