Disable DCHECK for no BLOCK_SHUTDOWN posted after TaskScheduler shutdown.

base/task_scheduler/task_tracker.cc

 // Copyright 2016 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/task_scheduler/task_tracker.h"
 
 #include <limits>
 #include <string>
 
 #include "base/callback.h"
@@ skipping 387 matching lines @@
     // and the moment they complete their execution.
     const bool shutdown_started = state_->IncrementNumTasksBlockingShutdown();
 
     if (shutdown_started) {
       AutoSchedulerLock auto_lock(shutdown_lock_);
 
       // A BLOCK_SHUTDOWN task posted after shutdown has completed is an
       // ordering bug. This aims to catch those early.
       DCHECK(shutdown_event_);
       if (shutdown_event_->IsSignaled()) {
+#if DCHECK_IS_ON()
+// clang-format off
         // TODO(robliao): http://crbug.com/698140. Since the service thread
         // doesn't stop processing its own tasks at shutdown, we may still
         // attempt to post a BLOCK_SHUTDOWN task in response to a
-        // FileDescriptorWatcher.
-#if DCHECK_IS_ON()
-        DCHECK(IsPostingBlockShutdownTaskAfterShutdownAllowed());
+        // FileDescriptorWatcher. Same is true for FilePathWatcher
+        // (http://crbug.com/728235). Until it's possible for such services to
+        // post to non-BLOCK_SHUTDOWN sequences which are themselves funneled to
+        // the main execution sequence (a future plan for the post_task.h API),
+        // this DCHECK will be flaky and must be disabled.
+        // DCHECK(IsPostingBlockShutdownTaskAfterShutdownAllowed());
+// clang-format on
 #endif
         state_->DecrementNumTasksBlockingShutdown();
         return false;
       }
 
       ++num_block_shutdown_tasks_posted_during_shutdown_;
 
       if (num_block_shutdown_tasks_posted_during_shutdown_ ==
           kMaxBlockShutdownTasksPostedDuringShutdown) {
         // Record the TaskScheduler.BlockShutdownTasksPostedDuringShutdown
@@ skipping 92 matching lines @@
   task_latency_histograms_[static_cast<int>(task->traits.priority())]
                           [task->traits.may_block() ||
                                    task->traits.with_base_sync_primitives()
                                ? 1
                                : 0]
                               ->Add(task_latency.InMicroseconds());
 }
 
 }  // namespace internal
 }  // namespace base