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

content/browser/renderer_host/media/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_BUILDABLE_VIDEO_CAPTURE_DEVICE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_BUILDABLE_VIDEO_CAPTURE_DEVICE_H_
 
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "content/browser/renderer_host/media/ownership.h"
 #include "content/public/common/media_stream_request.h"
 #include "media/capture/video/video_capture_device.h"
 #include "media/capture/video_capture_types.h"
 
 namespace content {
 
 class VideoCaptureController;
 
 class CONTENT_EXPORT BuildableDeviceCallbacks {
  public:
   virtual ~BuildableDeviceCallbacks() {}
   // Returns false if no descriptor was found.
   virtual const media::VideoCaptureDeviceDescriptor* LookupDeviceDescriptor(
       const std::string& id) = 0;
   virtual void WillStartDevice(media::VideoFacingMode facing_mode) = 0;
   virtual void DidStartDevice(VideoCaptureController* entry) = 0;
   virtual void OnDeviceStartFailed(VideoCaptureController* entry) = 0;
+  virtual void OnDeviceStartAborted() = 0;
 };
 
 // Abstraction for a video capture device that must be "built" before it can be
 // operated and must be "stopped", before it can be released. Typical operation
 // is that a newly created instance initially reports IsDeviceAlive() == false.
 // Clients call CreateAndStartDeviceAsync(), which kicks off the asynchronous
 // building of the device. The outcome of the device building is typically
 // reported to an instance of BuildableDeviceCallbacks (see above). Once the
 // device has been built successfully, the "Device operation methods", are
 // allowed to be called. ReleaseDeviceAsync() must be called in order to
-// release the device if it has before been built successfully. After calling
-// ReleaseDeviceAsync(), it is legal to call CreateAndStartDeviceAsync() to
-// rebuild and start the device again.
+// release the device if it has before been built successfully.
+// Clients may call ReleaseDeviceAsync() before a preceding call to
+// CreateAndStartDeviceAsync() has resulted in a callback to OnDeviceStarted()
+// or OnDeviceStartFailed(). Doing so requests the device startup to be aborted,
+// and the BuildableVideoCaptureDevice will call OnDeviceStartAborted() to
+// indicate when the abort is completed.
+// After calling ReleaseDeviceAsync(), it is legal to call
+// CreateAndStartDeviceAsync() to rebuild and start the device again.
 class BuildableVideoCaptureDevice {
  public:
   virtual ~BuildableVideoCaptureDevice() {}
 
   // Device management methods.
   // The passed-in |context_reference| must guarantee that the context relevant
   // during the asynchronous processing stays alive.
   virtual void CreateAndStartDeviceAsync(
       VideoCaptureController* controller,
       const media::VideoCaptureParams& params,
@@ skipping 23 matching lines @@
   // The passed-in |context_reference| must guarantee that the context relevant
   // during the asynchronous processing stays alive.
   virtual void SetDesktopCaptureWindowIdAsync(
       gfx::NativeViewId window_id,
       std::unique_ptr<Ownership> context_reference) = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_BUILDABLE_VIDEO_CAPTURE_DEVICE_H_