Ensure MessagePumpForUI doesn't run tasks after being aborted.

The previous behaviour of MessagePumpForUI::Abort was to prevent
delayed tasks from running, but non-delayed tasks would continue to run.
This was almost certainly not intentional, and an aborted pump probably
shouldn't be running any tasks at all.

Bug: 780100
Change-Id: I56ad5b0b5d0621450fc62a35c4d927f4975ae6a4
Reviewed-on: https://chromium-review.googlesource.com/748979Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513303}

base/message_loop/message_loop_unittest.cc

@@ -264,6 +264,10 @@ void AbortMessagePump() {
   static_cast<base::MessageLoopForUI*>(base::MessageLoop::current())->Abort();
 }
 
+void DoNotRun() {
+  ASSERT_TRUE(false);
+}
+
 void RunTest_AbortDontRunMoreTasks(bool delayed, bool init_java_first) {
   WaitableEvent test_done_event(WaitableEvent::ResetPolicy::MANUAL,
                                 WaitableEvent::InitialState::NOT_SIGNALED);
@@ -286,6 +290,8 @@ void RunTest_AbortDontRunMoreTasks(bool delayed, bool init_java_first) {
   } else {
     java_thread->message_loop()->task_runner()->PostTask(
         FROM_HERE, BindOnce(&AbortMessagePump));
+    java_thread->message_loop()->task_runner()->PostTask(FROM_HERE,
+                                                         BindOnce(&DoNotRun));
   }
 
   // Wait to ensure we catch the correct exception (and don't crash)

base/message_loop/message_pump_android.cc

@@ -35,6 +35,11 @@ static void DoRunLoopOnce(JNIEnv* env,
   base::MessagePumpForUI* pump =
       reinterpret_cast<base::MessagePumpForUI*>(native_message_pump);
   DCHECK(pump);
+  // If the pump has been aborted, tasks may continue to be queued up, but
+  // shouldn't run.
+  if (pump->ShouldAbort())
+    return;
+
   // This is based on MessagePumpForUI::DoRunLoop() from desktop.
   // Note however that our system queue is handled in the java side.
   // In desktop we inspect and process a single system message and then