Bug 1191145 - Stop blocking scripts when handling IPC messages (r=dvander)

dom/ipc/ContentChild.cpp

@@ -673,10 +673,6 @@ ContentChild::Init(MessageLoop* aIOLoop,
   }
   sSingleton = this;
 
-  // Make sure there's an nsAutoScriptBlocker on the stack when dispatching
-  // urgent messages.
-  GetIPCChannel()->BlockScripts();
-
   // If communications with the parent have broken down, take the process
   // down so it's not hanging around.
   bool abortOnError = true;

ipc/glue/MessageChannel.cpp

@@ -280,31 +280,6 @@ private:
     CxxStackFrame& operator=(const CxxStackFrame&) = delete;
 };
 
-namespace {
-
-class MOZ_RAII MaybeScriptBlocker {
-public:
-    explicit MaybeScriptBlocker(MessageChannel *aChannel, bool aBlock
-                                MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
-        : mBlocked(aChannel->ShouldBlockScripts() && aBlock)
-    {
-        MOZ_GUARD_OBJECT_NOTIFIER_INIT;
-        if (mBlocked) {
-            nsContentUtils::AddScriptBlocker();
-        }
-    }
-    ~MaybeScriptBlocker() {
-        if (mBlocked) {
-            nsContentUtils::RemoveScriptBlocker();
-        }
-    }
-private:
-    MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
-    bool mBlocked;
-};
-
-} // namespace
-
 MessageChannel::MessageChannel(MessageListener *aListener)
   : mListener(aListener),
     mChannelState(ChannelClosed),
@@ -332,7 +307,6 @@ MessageChannel::MessageChannel(MessageListener *aListener)
     mSawInterruptOutMsg(false),
     mIsWaitingForIncoming(false),
     mAbortOnError(false),
-    mBlockScripts(false),
     mFlags(REQUIRE_DEFAULT),
     mPeerPidSet(false),
     mPeerPid(-1)
@@ -868,9 +842,6 @@ MessageChannel::Send(Message* aMsg, Message* aReply)
 {
     nsAutoPtr<Message> msg(aMsg);
 
-    // See comment in DispatchSyncMessage.
-    MaybeScriptBlocker scriptBlocker(this, true);
-
     // Sanity checks.
     AssertWorkerThread();
     mMonitor->AssertNotCurrentThreadOwns();
@@ -1430,15 +1401,10 @@ MessageChannel::DispatchSyncMessage(const Message& aMsg, Message*& aReply)
 
     int prio = aMsg.priority();
 
-    // We don't want to run any code that might run a nested event loop here, so
-    // we avoid running event handlers. Once we've sent the response to the
-    // urgent message, it's okay to run event handlers again since the parent is
-    // no longer blocked.
     MOZ_ASSERT_IF(prio > IPC::Message::PRIORITY_NORMAL, NS_IsMainThread());
-    MaybeScriptBlocker scriptBlocker(this, prio > IPC::Message::PRIORITY_NORMAL);
 
     MessageChannel* dummy;
-    MessageChannel*& blockingVar = ShouldBlockScripts() ? gParentProcessBlocker : dummy;
+    MessageChannel*& blockingVar = mSide == ChildSide && NS_IsMainThread() ? gParentProcessBlocker : dummy;
 
     Result rv;
     {
@@ -1978,13 +1944,6 @@ MessageChannel::CloseWithTimeout()
     mChannelState = ChannelTimeout;
 }
 
-void
-MessageChannel::BlockScripts()
-{
-    MOZ_ASSERT(NS_IsMainThread());
-    mBlockScripts = true;
-}
-
 void
 MessageChannel::Close()
 {

ipc/glue/MessageChannel.h

@@ -120,13 +120,6 @@ class MessageChannel : HasResultCodes
     void SetChannelFlags(ChannelFlags aFlags) { mFlags = aFlags; }
     ChannelFlags GetChannelFlags() { return mFlags; }
 
-    void BlockScripts();
-
-    bool ShouldBlockScripts() const
-    {
-        return mBlockScripts;
-    }
-
     // Asynchronously send a message to the other side of the channel
     bool Send(Message* aMsg);
 
@@ -776,9 +769,6 @@ class MessageChannel : HasResultCodes
     // a channel error occurs?
     bool mAbortOnError;
 
-    // Should we prevent scripts from running while dispatching urgent messages?
-    bool mBlockScripts;
-
     // See SetChannelFlags
     ChannelFlags mFlags;