Mac QTKit Video Capture: Run QTCaptureSession teardown in UI thread, clean up -stopCapture use.

media/video/capture/mac/platform_video_capturing_mac.h

 // Copyright 2013 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 MEDIA_VIDEO_CAPTURE_MAC_PLATFORM_VIDEO_CAPTURING_MAC_H_
 #define MEDIA_VIDEO_CAPTURE_MAC_PLATFORM_VIDEO_CAPTURING_MAC_H_
 
 #import <Foundation/Foundation.h>
 
 namespace media {
 class VideoCaptureDeviceMac;
 }
 
 // Protocol representing platform-dependent video capture on Mac, implemented
 // by both QTKit and AVFoundation APIs.
 @protocol PlatformVideoCapturingMac <NSObject>
 
 // This method initializes the instance by calling NSObject |init| and registers
 // internally a frame receiver at the same time. The frame receiver is supposed
 // to be initialised before and outlive the VideoCapturingDeviceMac
 // implementation.
 - (id)initWithFrameReceiver:(media::VideoCaptureDeviceMac*)frameReceiver;
 
-// Set the frame receiver. This method executes the registration in mutual
+// Sets the frame receiver. This method executes the registration in mutual
 // exclusion.
 // TODO(mcasas): This method and stopCapture() are always called in sequence and
 // this one is only used to clear the frameReceiver, investigate if both can be
 // merged.
 - (void)setFrameReceiver:(media::VideoCaptureDeviceMac*)frameReceiver;
 
 // Sets which capture device to use by name passed as deviceId argument. The
 // device names are usually obtained via VideoCaptureDevice::GetDeviceNames()
 // method. This method will also configure all device properties except those in
-// setCaptureHeight:widht:frameRate. If |deviceId| is nil, all potential
-// configuration is torn down. Returns YES on sucess, NO otherwise.
+// setCaptureHeight:width:frameRate. If |deviceId| is nil, capture is stopped
+// and all potential configuration is torn down. Returns YES on sucess, NO
+// otherwise.
 - (BOOL)setCaptureDevice:(NSString*)deviceId;
 
 // Configures the capture properties.
 - (BOOL)setCaptureHeight:(int)height
                    width:(int)width
                frameRate:(float)frameRate;
 
-// Start video capturing, register observers. Returns YES on sucess, NO
+// Starts video capturing, registers observers. Returns YES on sucess, NO
 // otherwise.
 - (BOOL)startCapture;
 
 // Stops video capturing, unregisters observers.
 - (void)stopCapture;
 
 @end
 
 #endif  // MEDIA_VIDEO_CAPTURE_MAC_PLATFORM_VIDEO_CAPTURING_MAC_H_