Fix low frame rate problems in high resolution USB cameras using AVFoundation

media/capture/video/mac/video_capture_device_avfoundation_mac.mm

 // 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.
 
 #import "media/capture/video/mac/video_capture_device_avfoundation_mac.h"
 
 #import <AVFoundation/AVFoundation.h>
 #import <CoreMedia/CoreMedia.h>
 #import <CoreVideo/CoreVideo.h>
 #include <stddef.h>
@@ skipping 243 matching lines @@
     captureDevice_ = nil;
     [self sendErrorString:
               [NSString stringWithFormat:
                             @"Could not create video capture input (%@): %@",
                             [error localizedDescription],
                             [error localizedFailureReason]]];
     return NO;
   }
   [captureSession_ addInput:captureDeviceInput_];
 
+  // Create and plug the still image capture output. This should happen in
+  // advance of the actual picture to allow for the 3A to stabilize.
+  stillImageOutput_.reset([[AVCaptureStillImageOutput alloc] init]);
+  if (stillImageOutput_ && [captureSession_ canAddOutput:stillImageOutput_])
+    [captureSession_ addOutput:stillImageOutput_];
+
   // Create a new data output for video. The data output is configured to
   // discard late frames by default.
   captureVideoDataOutput_.reset([[AVCaptureVideoDataOutput alloc] init]);
   if (!captureVideoDataOutput_) {
     [captureSession_ removeInput:captureDeviceInput_];
     [self sendErrorString:[NSString stringWithUTF8String:
                                         "Could not create video data output."]];
     return NO;
   }
   [captureVideoDataOutput_ setAlwaysDiscardsLateVideoFrames:true];
   [captureVideoDataOutput_
       setSampleBufferDelegate:self
                         queue:dispatch_get_global_queue(
                                   DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)];
   [captureSession_ addOutput:captureVideoDataOutput_];
 
-  // Create and plug the still image capture output. This should happen in
-  // advance of the actual picture to allow for the 3A to stabilize.
-  stillImageOutput_.reset([[AVCaptureStillImageOutput alloc] init]);
-  if (stillImageOutput_ && [captureSession_ canAddOutput:stillImageOutput_])
-    [captureSession_ addOutput:stillImageOutput_];
-
   return YES;
 }
 
 - (BOOL)setCaptureHeight:(int)height
                    width:(int)width
                frameRate:(float)frameRate {
   DCHECK(![captureSession_ isRunning] &&
          main_thread_checker_.CalledOnValidThread());
 
   frameWidth_ = width;
@@ skipping 194 matching lines @@
 }
 
 - (void)sendErrorString:(NSString*)error {
   DLOG(ERROR) << [error UTF8String];
   base::AutoLock lock(lock_);
   if (frameReceiver_)
     frameReceiver_->ReceiveError(FROM_HERE, [error UTF8String]);
 }
 
 @end