sync: don't notify from ~BaseTransaction if the writer is INVALID.

chrome/browser/sync/util/dbgq.h

-// Copyright (c) 2009 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 CHROME_BROWSER_SYNC_UTIL_DBGQ_H_
-#define CHROME_BROWSER_SYNC_UTIL_DBGQ_H_
-#pragma once
-
-#include "base/basictypes.h"  // for COMPILE_ASSERT
-
-// A circular queue that is designed to be easily inspectable in a debugger. It
-// puts the elements into the array in reverse, so you can just look at the i_
-// pointer for a recent history.
-template <typename T, size_t size>
-class DebugQueue {
-  COMPILE_ASSERT(size > 0, DebugQueue_size_must_be_greater_than_zero);
- public:
-  DebugQueue() : i_(array_) { }
-  void Push(const T& t) {
-    i_ = (array_ == i_ ? array_ + size - 1 : i_ - 1);
-    *i_ = t;
-  }
- protected:
-  T* i_;  // Points to the newest element in the queue.
-  T array_[size];
-};
-
-#endif  // CHROME_BROWSER_SYNC_UTIL_DBGQ_H_