Close all active PeerConnections upon OS suspend (relanding r290125 and r291213)

content/renderer/media/peer_connection_tracker.h

Index: content/renderer/media/peer_connection_tracker.h
diff --git a/content/renderer/media/peer_connection_tracker.h b/content/renderer/media/peer_connection_tracker.h
index 8f3e16b42bd6b41273ca589f19cab2faa5dc0a9a..8a774cb7530f1ac7a710ddd954647a637a18ba72 100644
--- a/content/renderer/media/peer_connection_tracker.h
+++ b/content/renderer/media/peer_connection_tracker.h
@@ -163,6 +163,9 @@ class CONTENT_EXPORT PeerConnectionTracker : public RenderProcessObserver {
   // IPC Message handler for getting all stats.
   void OnGetAllStats();
 
+  // Called when the browser process reports a suspend event from the OS.
+  void OnSuspend();
+
   void SendPeerConnectionUpdate(RTCPeerConnectionHandler* pc_handler,
                                 const std::string& callback_type,
                                 const std::string& value);