Reland r52336.

base/message_loop.h

 // Copyright (c) 2006-2008 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.
 
 #ifndef BASE_MESSAGE_LOOP_H_
 #define BASE_MESSAGE_LOOP_H_
 
 #include <queue>
 #include <string>
 
 #include "base/basictypes.h"
-#include "base/histogram.h"
+#include "base/lock.h"
 #include "base/message_pump.h"
 #include "base/observer_list.h"
 #include "base/ref_counted.h"
-#include "base/scoped_ptr.h"
 #include "base/task.h"
 
 #if defined(OS_WIN)
 // We need this to declare base::MessagePumpWin::Dispatcher, which we should
 // really just eliminate.
 #include "base/message_pump_win.h"
 #elif defined(OS_POSIX)
 #include "base/message_pump_libevent.h"
 #if !defined(OS_MACOSX)
 #include "base/message_pump_glib.h"
 #endif
 #endif
 
+class Histogram;
+
 // A MessageLoop is used to process events for a particular thread.  There is
 // at most one MessageLoop instance per thread.
 //
 // Events include at a minimum Task instances submitted to PostTask or those
 // managed by TimerManager.  Depending on the type of message pump used by the
 // MessageLoop other events such as UI messages may be processed.  On Windows
 // APC calls (as time permits) and signals sent to a registered set of HANDLEs
 // may also be processed.
 //
 // NOTE: Unless otherwise specified, a MessageLoop's methods may only be called
@@ skipping 380 matching lines @@
 
   // Start recording histogram info about events and action IF it was enabled
   // and IF the statistics recorder can accept a registration of our histogram.
   void StartHistogrammer();
 
   // Add occurence of event to our histogram, so that we can see what is being
   // done in a specific MessageLoop instance (i.e., specific thread).
   // If message_histogram_ is NULL, this is a no-op.
   void HistogramEvent(int event);
 
-  static const LinearHistogram::DescriptionPair event_descriptions_[];
-  static bool enable_histogrammer_;
-
   Type type_;
 
   // A list of tasks that need to be processed by this instance.  Note that
   // this queue is only accessed (push/pop) by our current thread.
   TaskQueue work_queue_;
 
   // Contains delayed tasks, sorted by their 'delayed_run_time' property.
   DelayedTaskQueue delayed_work_queue_;
 
   // A queue of non-nestable tasks that we had to defer because when it came
@@ skipping 152 matching lines @@
 #endif  // defined(OS_POSIX)
 };
 
 // Do not add any member variables to MessageLoopForIO!  This is important b/c
 // MessageLoopForIO is often allocated via MessageLoop(TYPE_IO).  Any extra
 // data that you need should be stored on the MessageLoop's pump_ instance.
 COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
                MessageLoopForIO_should_not_have_extra_member_variables);
 
 #endif  // BASE_MESSAGE_LOOP_H_