Bug 1268160: Assert that PostIdleTask is only used on the main thread. r=jld

ipc/chromium/src/base/message_loop.cc

@@ -271,6 +271,7 @@ void MessageLoop::PostDelayedTask(already_AddRefed<Runnable> task, int delay_ms)
 
 void MessageLoop::PostIdleTask(already_AddRefed<Runnable> task) {
   DCHECK(current() == this);
+  MOZ_ASSERT(NS_IsMainThread());
 
   PendingTask pending_task(Move(task), false);
   deferred_non_nestable_work_queue_.push(Move(pending_task));

ipc/glue/MessagePump.cpp

@@ -356,7 +356,8 @@ MessagePumpForNonMainThreads::Run(base::MessagePump::Delegate* aDelegate)
       continue;
     }
 
-    didWork = aDelegate->DoIdleWork();
+    DebugOnly<bool> didIdleWork = aDelegate->DoIdleWork();
+    MOZ_ASSERT(!didIdleWork);
     if (!keep_running_) {
       break;
     }
@@ -418,7 +419,8 @@ MessagePumpForNonMainUIThreads::DoRunLoop()
       continue;
     }
 
-    didWork = state_->delegate->DoIdleWork();
+    DebugOnly<bool> didIdleWork = state_->delegate->DoIdleWork();
+    MOZ_ASSERT(!didIdleWork);
     CHECK_QUIT_STATE
 
     SetInWait();

xpcom/base/nsIMessageLoop.idl

@@ -13,8 +13,8 @@ interface nsIRunnable;
  * or may not make sense for you to use this interface.  If you're calling from
  * JS, you don't have a choice!
  *
- * Right now, you can only call PostIdleTask(), but nothing is stopping you
- * from adding other methods.
+ * Right now, you can only call PostIdleTask(), and the wrath of khuey is
+ * stopping you from adding other methods.
  *
  * nsIMessageLoop's contractid is "@mozilla.org/message-loop;1".
  */