Bug 554262 - [OOPP] Silverlight context menu hangs the browser. r=bent, jmathies.

ipc/glue/RPCChannel.cpp

@@ -204,7 +204,11 @@ RPCChannel::Call(Message* msg, Message* reply)
         while (!EventOccurred()) {
             bool maybeTimedOut = !RPCChannel::WaitForNotify();
 
-            if (EventOccurred())
+            if (EventOccurred() ||
+                // we might have received a "subtly deferred" message
+                // in a nested loop that it's now time to process
+                (!maybeTimedOut &&
+                 (!mDeferred.empty() || !mOutOfTurnReplies.empty())))
                 break;
 
             if (maybeTimedOut && !ShouldContinueFromTimeout())
@@ -224,10 +228,18 @@ RPCChannel::Call(Message* msg, Message* reply)
             recvd = it->second;
             mOutOfTurnReplies.erase(it);
         }
-        else {
+        else if (!mPending.empty()) {
             recvd = mPending.front();
             mPending.pop();
         }
+        else {
+            // because of subtleties with nested event loops, it's
+            // possible that we got here and nothing happened.  or, we
+            // might have a deferred in-call that needs to be
+            // processed.  either way, we won't break the inner while
+            // loop again until something new happens.
+            continue;
+        }
 
         if (!recvd.is_sync() && !recvd.is_rpc()) {
             MutexAutoUnlock unlock(mMutex);

ipc/glue/WindowsMessageLoop.cpp

@@ -658,6 +658,8 @@ RPCChannel::SpinInternalEventLoop()
       } else {
           TranslateMessage(&msg);
           DispatchMessageW(&msg);
+          ExitSpinLoop();
+          return false;
       }
     } else {
       // Block and wait for any posted application messages