Record async "task backtraces"

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 108 matching lines @@
     : type_(type),
 #if defined(OS_WIN)
       pending_high_res_tasks_(0),
       in_high_res_mode_(false),
 #endif
       nestable_tasks_allowed_(true),
 #if defined(OS_WIN)
       os_modal_loop_(false),
 #endif  // OS_WIN
       message_histogram_(NULL),
-      run_loop_(NULL) {
+      run_loop_(NULL),
+      current_pending_task_(NULL) {
   Init();
 
   pump_ = CreateMessagePumpForType(type).Pass();
 }
 
 MessageLoop::MessageLoop(scoped_ptr<MessagePump> pump)
     : pump_(pump.Pass()),
       type_(TYPE_CUSTOM),
 #if defined(OS_WIN)
       pending_high_res_tasks_(0),
@@ skipping 279 matching lines @@
 
   PendingTask pending_task = deferred_non_nestable_work_queue_.front();
   deferred_non_nestable_work_queue_.pop();
 
   RunTask(pending_task);
   return true;
 }
 
 void MessageLoop::RunTask(const PendingTask& pending_task) {
   DCHECK(nestable_tasks_allowed_);
+  current_pending_task_ = &pending_task;
 
 #if defined(OS_WIN)
   if (pending_task.is_high_res) {
     pending_high_res_tasks_--;
     CHECK_GE(pending_high_res_tasks_, 0);
   }
 #endif
 
   // Execute the task and assume the worst: It is probably not reentrant.
   nestable_tasks_allowed_ = false;
 
   HistogramEvent(kTaskRunEvent);
 
   FOR_EACH_OBSERVER(TaskObserver, task_observers_,
                     WillProcessTask(pending_task));
   task_annotator_.RunTask(
       "MessageLoop::PostTask", "MessageLoop::RunTask", pending_task);
   FOR_EACH_OBSERVER(TaskObserver, task_observers_,
                     DidProcessTask(pending_task));
 
   nestable_tasks_allowed_ = true;
+
+  current_pending_task_ = NULL;
 }
 
 bool MessageLoop::DeferOrRunPendingTask(const PendingTask& pending_task) {
   if (pending_task.nestable || run_loop_->run_depth_ == 1) {
     RunTask(pending_task);
     // Show that we ran a task (Note: a new one might arrive as a
     // consequence!).
     return true;
   }
 
@@ skipping 251 matching lines @@
       persistent,
       mode,
       controller,
       delegate);
 }
 #endif
 
 #endif  // !defined(OS_NACL_SFI)
 
 }  // namespace base