Bug 1487419 - Save current desktop configuration in ScreenCapturerMac::Init; r=pehrsons

Summary:
The fix for Bug 1409018 accidentally removed saving the current desktop
configuration during Init() which causes it to not be set when a different
screen is selected, meaning that regardless of the choice made, only the
first screen is captured.

Reviewers: pehrsons

Tags: #secure-revision

Bug #: 1487419

Differential Revision: https://phabricator.services.mozilla.com/D5062

--HG--
extra : rebase_source : bb4f9a0f4e06dfbd9730b7af4a0748749d72c3da

media/webrtc/trunk/webrtc/modules/desktop_capture/screen_capturer_mac.mm

@@ -424,6 +424,7 @@ bool ScreenCapturerMac::Init() {
   ScreenConfigurationChanged();
 */
   desktop_config_monitor_->Lock();
+  desktop_config_ = desktop_config_monitor_->desktop_configuration();
   update_screen_configuration_ = true;
   desktop_config_monitor_->Unlock();
   return true;