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

content/browser/browser_main_loop.h

Index: content/browser/browser_main_loop.h
diff --git a/content/browser/browser_main_loop.h b/content/browser/browser_main_loop.h
index 5c16af450e49771d922d69ad4a73488b6ff87569..e04999b005d883d02a5d07252152b5b212d5e26a 100644
--- a/content/browser/browser_main_loop.h
+++ b/content/browser/browser_main_loop.h
@@ -101,6 +101,12 @@ class CONTENT_EXPORT BrowserMainLoop {
 
   bool is_tracing_startup() const { return is_tracing_startup_; }
 
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+  DeviceMonitorMac* device_monitor_mac() const {
+    return device_monitor_mac_.get();
+  }
+#endif
+
  private:
   class MemoryObserver;
   // For ShutdownThreadsAndCleanUp.