[Mojo Video Capture] Simplify API and some cleanups

services/video_capture/mock_device_descriptor_receiver.h

 // Copyright 2016 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 SERVICES_VIDEO_CAPTURE_MOCK_DEVICE_DESCRIPTOR_RECEIVER_H_
 #define SERVICES_VIDEO_CAPTURE_MOCK_DEVICE_DESCRIPTOR_RECEIVER_H_
 
 #include "services/video_capture/public/interfaces/video_capture_device_factory.mojom.h"
 #include "testing/gmock/include/gmock/gmock.h"
 
 namespace video_capture {
 
+// Mock for receiving device descriptors from a call to
+// mojom::VideoCaptureDeviceFactory::EnumerateDeviceDescriptors().
 class MockDeviceDescriptorReceiver {
  public:
   MockDeviceDescriptorReceiver();
   ~MockDeviceDescriptorReceiver();
 
   // Use forwarding method to work around gmock not supporting move-only types.
   void HandleEnumerateDeviceDescriptorsCallback(
       std::vector<mojom::VideoCaptureDeviceDescriptorPtr> descriptors);
 
   MOCK_METHOD1(
       OnEnumerateDeviceDescriptorsCallback,
       void(const std::vector<mojom::VideoCaptureDeviceDescriptorPtr>&));
 };
 
 }  // namespace video_capture
 
 #endif  // SERVICES_VIDEO_CAPTURE_MOCK_DEVICE_DESCRIPTOR_RECEIVER_H_