Use WeakPtr for RTCPeerConnectionHandler and RTCPeerConnectionTracker.

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 9f8e6847687834d60ce4bf62159f0252c667dd4e..08f908607fe97edfd2fc8dbf79fc0003a5c664b8 100644
--- a/content/renderer/media/peer_connection_tracker.h
+++ b/content/renderer/media/peer_connection_tracker.h
@@ -8,6 +8,7 @@
 #include <map>
 
 #include "base/compiler_specific.h"
+#include "base/memory/weak_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "content/public/renderer/render_process_observer.h"
 #include "third_party/WebKit/public/platform/WebMediaStream.h"
@@ -34,7 +35,9 @@ class RTCPeerConnectionHandler;
 // This class collects data about each peer connection,
 // sends it to the browser process, and handles messages
 // from the browser process.
-class CONTENT_EXPORT PeerConnectionTracker : public RenderProcessObserver {
+class CONTENT_EXPORT PeerConnectionTracker
+    : public RenderProcessObserver,
+      public base::SupportsWeakPtr<PeerConnectionTracker> {
  public:
   PeerConnectionTracker();
   ~PeerConnectionTracker() override;