Add null check for MediaDevicesManager in MDDH destructor.

content/browser/renderer_host/media/media_devices_dispatcher_host.cc

Index: content/browser/renderer_host/media/media_devices_dispatcher_host.cc
diff --git a/content/browser/renderer_host/media/media_devices_dispatcher_host.cc b/content/browser/renderer_host/media/media_devices_dispatcher_host.cc
index d50e28a78e27a0f99215783ad6e34aad1ac3e0e1..32ce8dcf11910a755584b12aa9ae727bfe189ee7 100644
--- a/content/browser/renderer_host/media/media_devices_dispatcher_host.cc
+++ b/content/browser/renderer_host/media/media_devices_dispatcher_host.cc
@@ -96,7 +96,8 @@ MediaDevicesDispatcherHost::MediaDevicesDispatcherHost(
 MediaDevicesDispatcherHost::~MediaDevicesDispatcherHost() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   for (size_t i = 0; i < NUM_MEDIA_DEVICE_TYPES; ++i) {
-    if (!device_change_subscriptions_[i].empty()) {
+    if (media_stream_manager_->media_devices_manager() &&

[tommi (sloooow) - chröme, 2017/01/03 13:13:20]

would it make sense to do this check outside the for loop?

[Guido Urdaneta, 2017/01/03 13:27:17]

Done.

+        !device_change_subscriptions_[i].empty()) {
       media_stream_manager_->media_devices_manager()
           ->UnsubscribeDeviceChangeNotifications(
               static_cast<MediaDeviceType>(i), this);