[Mojo Video Capture] Add support to BuildableVideoCaptureDevice for aborting the device start.

content/browser/renderer_host/media/in_process_buildable_video_capture_device.h

 // Copyright 2017 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_BROWSER_RENDERER_HOST_MEDIA_IN_PROCESS_BUILDABLE_VIDEO_CAPTURE_DEVICE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_IN_PROCESS_BUILDABLE_VIDEO_CAPTURE_DEVICE_H_
 
 #include "content/browser/renderer_host/media/video_capture_controller.h"
 #include "content/public/common/media_stream_request.h"
 #include "media/capture/video/video_capture_device.h"
@@ skipping 38 matching lines @@
   void RequestRefreshFrame() override;
 
   void SetDesktopCaptureWindowIdAsync(
       gfx::NativeViewId window_id,
       std::unique_ptr<Ownership> context_reference) override;
 
  private:
   using ReceiveDeviceCallback =
       base::Callback<void(std::unique_ptr<media::VideoCaptureDevice> device)>;
 
+  enum class State {
+    NO_DEVICE,
+    DEVICE_START_IN_PROGRESS,
+    DEVICE_START_ABORTING,
+    DEVICE_STARTED
+  };
+
   std::unique_ptr<media::VideoCaptureDeviceClient> CreateDeviceClient(
       int buffer_pool_max_buffer_count,
       base::WeakPtr<media::VideoFrameReceiver> receiver);
 
   void OnDeviceStarted(VideoCaptureController* controller,
                        BuildableDeviceCallbacks* callbacks,
                        std::unique_ptr<Ownership> ownership,
                        std::unique_ptr<media::VideoCaptureDevice> device);
 
   void DoStartDeviceCaptureOnDeviceThread(
@@ skipping 15 matching lines @@
       ReceiveDeviceCallback result_callback);
 
   void SetDesktopCaptureWindowIdOnDeviceThread(
       media::VideoCaptureDevice* device,
       gfx::NativeViewId window_id,
       std::unique_ptr<Ownership> ownership);
 
   const scoped_refptr<base::SingleThreadTaskRunner> device_task_runner_;
   media::VideoCaptureDeviceFactory* const device_factory_;
   std::unique_ptr<media::VideoCaptureDevice> device_;
+  State state_ = State::NO_DEVICE;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_IN_PROCESS_BUILDABLE_VIDEO_CAPTURE_DEVICE_H_