When stopping QTKit video capture, call stopRunning before removeInput:.

media/video/capture/mac/video_capture_device_qtkit_mac.mm

 // Copyright (c) 2012 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.
 
 #import "media/video/capture/mac/video_capture_device_qtkit_mac.h"
 
 #import <QTKit/QTKit.h>
 
 #include "base/debug/crash_logging.h"
 #include "base/logging.h"
@@ skipping 201 matching lines @@
                            selector:@selector(handleNotification:)
                                name:QTCaptureSessionRuntimeErrorNotification
                              object:captureSession_];
     [captureSession_ startRunning];
   }
   return YES;
 }
 
 - (void)stopCapture {
   if ([[captureSession_ inputs] count] == 1) {
+    // |stopRunning| must be called before |removeInput:| to avoid a deadlock
+    // with device enumeration when the active camera is unplugged.
+    [captureSession_ stopRunning];
     [captureSession_ removeInput:captureDeviceInput_];
-    [captureSession_ stopRunning];
   }
 
   [[NSNotificationCenter defaultCenter] removeObserver:self];
 }
 
 // |captureOutput| is called by the capture device to deliver a new frame.
 - (void)captureOutput:(QTCaptureOutput*)captureOutput
   didOutputVideoFrame:(CVImageBufferRef)videoFrame
      withSampleBuffer:(QTSampleBuffer*)sampleBuffer
        fromConnection:(QTCaptureConnection*)connection {
@@ skipping 72 matching lines @@
   [lock_ unlock];
 }
 
 - (void)handleNotification:(NSNotification*)errorNotification {
   NSError * error = (NSError*)[[errorNotification userInfo]
       objectForKey:QTCaptureSessionErrorKey];
   frameReceiver_->ReceiveError([[error localizedDescription] UTF8String]);
 }
 
 @end