Bug 1755318: Move the RemovePeerConnection call to Close. r=mjf

This avoids the situation where PeerConnectionCtx is holding onto bare pointers
to PeerConnectionImpl whose refcounts have gone to 0, which is a pretty big
footgun.

Differential Revision: https://phabricator.services.mozilla.com/D139214

dom/media/webrtc/jsapi/PeerConnectionImpl.cpp

@@ -384,12 +384,6 @@ PeerConnectionImpl::~PeerConnectionImpl() {
     mTimeCard = nullptr;
   }
 
-  if (PeerConnectionCtx::isActive()) {
-    PeerConnectionCtx::GetInstance()->RemovePeerConnection(mHandle);
-  } else {
-    CSFLogError(LOGTAG, "PeerConnectionCtx is already gone. Ignoring...");
-  }
-
   CSFLogInfo(LOGTAG, "%s: PeerConnectionImpl destructor invoked for %s",
              __FUNCTION__, mHandle.c_str());
 }
@@ -1891,6 +1885,7 @@ PeerConnectionImpl::Close() {
     return NS_OK;
   }
 
+  STAMP_TIMECARD(mTimeCard, "Close");
   mSignalingState = RTCSignalingState::Closed;
 
   // When ICE completes, we record a bunch of statistics that outlive the
@@ -1999,6 +1994,12 @@ PeerConnectionImpl::Close() {
             }
           });
 
+  if (PeerConnectionCtx::isActive()) {
+    // If we're shutting down xpcom, this Instance will be unset before calling
+    // Close() on all remaining PCs, to avoid reentrancy.
+    PeerConnectionCtx::GetInstance()->RemovePeerConnection(mHandle);
+  }
+
   return NS_OK;
 }