Mac AVFoundation/QTKit: delay DeviceMonitorMac startup to first GetUserMedia.

content/browser/renderer_host/media/media_stream_manager.cc

 // 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.
 
 #include "content/browser/renderer_host/media/media_stream_manager.h"
 
 #include <list>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 24 matching lines @@
 #include "media/audio/audio_parameters.h"
 #include "media/base/channel_layout.h"
 #include "url/gurl.h"
 
 #if defined(OS_WIN)
 #include "base/win/scoped_com_initializer.h"
 #endif
 
 namespace content {
 
+// Forward declaration of DeviceMonitorMac and its only useable method.
+class DeviceMonitorMac {
+ public:
+  void StartMonitoring();
+};
+
 namespace {
 // Creates a random label used to identify requests.
 std::string RandomLabel() {
   // An earlier PeerConnection spec,
   // http://dev.w3.org/2011/webrtc/editor/webrtc.html, specified the
   // MediaStream::label alphabet as containing 36 characters from
   // range: U+0021, U+0023 to U+0027, U+002A to U+002B, U+002D to U+002E,
   // U+0030 to U+0039, U+0041 to U+005A, U+005E to U+007E.
   // Here we use a safe subset.
   static const char kAlphabet[] = "0123456789"
@@ skipping 722 matching lines @@
 
   monitoring_started_ = true;
   base::SystemMonitor::Get()->AddDevicesChangedObserver(this);
 
   // Enumerate both the audio and video devices to cache the device lists
   // and send them to media observer.
   ++active_enumeration_ref_count_[MEDIA_DEVICE_AUDIO_CAPTURE];
   audio_input_device_manager_->EnumerateDevices(MEDIA_DEVICE_AUDIO_CAPTURE);
   ++active_enumeration_ref_count_[MEDIA_DEVICE_VIDEO_CAPTURE];
   video_capture_manager_->EnumerateDevices(MEDIA_DEVICE_VIDEO_CAPTURE);
+
+#if defined(OS_MACOSX)
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&MediaStreamManager::StartMonitoringOnUIThread,
+                 base::Unretained(this)));
+#endif
 }
 
+#if defined(OS_MACOSX)
+void MediaStreamManager::StartMonitoringOnUIThread() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  BrowserMainLoop* browser_main_loop = content::BrowserMainLoop::GetInstance();
+  if (browser_main_loop)
+    browser_main_loop->device_monitor_mac()->StartMonitoring();
+}
+#endif
+
 void MediaStreamManager::StopMonitoring() {
   DCHECK_EQ(base::MessageLoop::current(), io_loop_);
   if (monitoring_started_) {
     base::SystemMonitor::Get()->RemoveDevicesChangedObserver(this);
     monitoring_started_ = false;
     ClearEnumerationCache(&audio_enumeration_cache_);
     ClearEnumerationCache(&video_enumeration_cache_);
   }
 }
 
@@ skipping 1017 matching lines @@
   }
 
   // Always do enumeration even though some enumeration is in progress,
   // because those enumeration commands could be sent before these devices
   // change.
   ++active_enumeration_ref_count_[stream_type];
   GetDeviceManager(stream_type)->EnumerateDevices(stream_type);
 }
 
 }  // namespace content