Bug 1389314 Part4: Disable the input priority event when shutting down. r=smaug.

MozReview-Commit-ID: CWV1kr3xMQL

dom/ipc/ContentParent.cpp

@@ -1389,12 +1389,15 @@ ContentParent::ShutDownProcess(ShutDownMethod aMethod)
   // other methods. We first call Shutdown() in the child. After the child is
   // ready, it calls FinishShutdown() on us. Then we close the channel.
   if (aMethod == SEND_SHUTDOWN_MESSAGE) {
-    if (mIPCOpen && !mShutdownPending && SendShutdown()) {
-      mShutdownPending = true;
-      // Start the force-kill timer if we haven't already.
-      StartForceKillTimer();
+    if (mIPCOpen && !mShutdownPending) {
+      // Stop sending input events with input priority when shutting down.
+      SetInputPriorityEventEnabled(false);
+      if (SendShutdown()) {
+        mShutdownPending = true;
+        // Start the force-kill timer if we haven't already.
+        StartForceKillTimer();
+      }
     }
-
     // If call was not successful, the channel must have been broken
     // somehow, and we will clean up the error in ActorDestroy.
     return;