Remove unnecessary inclusion of base/metrics/histogram.h

base/message_loop/incoming_task_queue.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/incoming_task_queue.h"
 
 #include <limits>
 
 #include "base/location.h"
 #include "base/message_loop/message_loop.h"
-#include "base/metrics/histogram.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 
 namespace base {
 namespace internal {
 
 namespace {
 
 #ifndef NDEBUG
@@ skipping 152 matching lines @@
   // After we've scheduled the message loop, we do not need to do so again
   // until we know it has processed all of the work in our queue and is
   // waiting for more work again. The message loop will always attempt to
   // reload from the incoming queue before waiting again so we clear this flag
   // in ReloadWorkQueue().
   message_loop_scheduled_ = true;
 }
 
 }  // namespace internal
 }  // namespace base