Mac: Add flag to force QTKit in otherwise AVFoundation-enabled builds/configs

media/video/capture/mac/avfoundation_glue.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/video/capture/mac/avfoundation_glue.h"
 
 #include <dlfcn.h>
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
@@ skipping 90 matching lines @@
 };
 
 }  // namespace
 
 static base::LazyInstance<AVFoundationInternal> g_avfoundation_handle =
     LAZY_INSTANCE_INITIALIZER;
 
 bool AVFoundationGlue::IsAVFoundationSupported() {
   // DeviceMonitorMac will initialize this static bool from the main UI thread
   // once, during Chrome startup so this construction is thread safe.
+  // Use AVFoundation if possible, enabled, and QTKit is not explicitly forced.
+  static CommandLine* command_line = CommandLine::ForCurrentProcess();
   static bool is_av_foundation_supported = base::mac::IsOSLionOrLater() &&
-      (CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableAVFoundation) ||
-          base::FieldTrialList::FindFullName("AVFoundationMacVideoCapture")
-              == "Enabled") && [AVFoundationBundle() load];
+      ((command_line->HasSwitch(switches::kEnableAVFoundation) &&
+      !command_line->HasSwitch(switches::kForceQTKit)) ||
+      base::FieldTrialList::FindFullName("AVFoundationMacVideoCapture")
+          == "Enabled") && [AVFoundationBundle() load];
   return is_av_foundation_supported;
 }
 
 NSBundle const* AVFoundationGlue::AVFoundationBundle() {
   return g_avfoundation_handle.Get().bundle();
 }
 
 void* AVFoundationGlue::AVFoundationLibraryHandle() {
   return g_avfoundation_handle.Get().library_handle();
 }
@@ skipping 71 matching lines @@
 @implementation AVCaptureDeviceInputGlue
 
 + (CrAVCaptureDeviceInput*)deviceInputWithDevice:(CrAVCaptureDevice*)device
                                            error:(NSError**)outError {
   return [[AVFoundationGlue::AVFoundationBundle()
       classNamed:@"AVCaptureDeviceInput"] deviceInputWithDevice:device
                                                           error:outError];
 }
 
 @end  // @implementation AVCaptureDeviceInputGlue