Pending tasks in a message loop should be deleted before shutting down Blink

base/message_loop/message_loop.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/message_loop/message_loop.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 145 matching lines @@
 }
 
 MessageLoop::~MessageLoop() {
   DCHECK_EQ(this, current());
 
   DCHECK(!run_loop_);
 #if defined(OS_WIN)
   if (in_high_res_mode_)
     Time::ActivateHighResolutionTimer(false);
 #endif
+
+  FlushPendingTasks();
+
+  // Let interested parties have one last shot at accessing this.
+  FOR_EACH_OBSERVER(DestructionObserver, destruction_observers_,
+                    WillDestroyCurrentMessageLoop());
+
+  thread_task_runner_handle_.reset();
+
+  // Tell the incoming queue that we are dying.
+  incoming_task_queue_->WillDestroyCurrentMessageLoop();
+  incoming_task_queue_ = NULL;
+  message_loop_proxy_ = NULL;
+
+  // OK, now make it so that no one can find us.
+  lazy_tls_ptr.Pointer()->Set(NULL);
+}
+
+void MessageLoop::FlushPendingTasks() {
   // Clean up any unprocessed tasks, but take care: deleting a task could
   // result in the addition of more tasks (e.g., via DeleteSoon).  We set a
   // limit on the number of times we will allow a deleted task to generate more
   // tasks.  Normally, we should only pass through this loop once or twice.  If
   // we end up hitting the loop limit, then it is probably due to one task that
   // is being stubborn.  Inspect the queues to see who is left.
   bool did_work;
   for (int i = 0; i < 100; ++i) {
     DeletePendingTasks();
     ReloadWorkQueue();
     // If we end up with empty queues, then break out of the loop.
     did_work = DeletePendingTasks();
     if (!did_work)
       break;
   }
   DCHECK(!did_work);
-
-  // Let interested parties have one last shot at accessing this.
-  FOR_EACH_OBSERVER(DestructionObserver, destruction_observers_,
-                    WillDestroyCurrentMessageLoop());
-
-  thread_task_runner_handle_.reset();
-
-  // Tell the incoming queue that we are dying.
-  incoming_task_queue_->WillDestroyCurrentMessageLoop();
-  incoming_task_queue_ = NULL;
-  message_loop_proxy_ = NULL;
-
-  // OK, now make it so that no one can find us.
-  lazy_tls_ptr.Pointer()->Set(NULL);
 }
 
 // static
 MessageLoop* MessageLoop::current() {
   // TODO(darin): sadly, we cannot enable this yet since people call us even
   // when they have no intention of using us.
   // DCHECK(loop) << "Ouch, did you forget to initialize me?";
   return lazy_tls_ptr.Pointer()->Get();
 }
 
@@ skipping 504 matching lines @@
       persistent,
       mode,
       controller,
       delegate);
 }
 #endif
 
 #endif  // !defined(OS_NACL)
 
 }  // namespace base