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diff --git a/chrome/browser/chrome_thread.h b/chrome/browser/chrome_thread.h
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+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef CHROME_BROWSER_CHROME_THREAD_H__
+#define CHROME_BROWSER_CHROME_THREAD_H__
+
+#include "base/lock.h"
+#include "base/logging.h"
+#include "base/thread.h"
+
+///////////////////////////////////////////////////////////////////////////////
+// ChromeThread
+//
+// This class represents a thread that is known by a browser-wide name.  For
+// example, there is one IO thread for the entire browser process, and various
+// pieces of code find it useful to retrieve a pointer to the IO thread's
+// MessageLoop by name:
+//
+//   MessageLoop* io_loop = ChromeThread::GetMessageLoop(ChromeThread::IO);
+//
+// On the UI thread, it is often preferable to obtain a pointer to a well-known
+// thread via the g_browser_process object, e.g. g_browser_process->io_thread();
+//
+// Code that runs on a thread other than the UI thread must take extra care in
+// handling pointers to threads because many of the well-known threads are owned
+// by the UI thread and can be deallocated without notice.
+//
+class ChromeThread : public Thread {
+ public:
+  // An enumeration of the well-known threads.
+  enum ID {
+    // This is the thread that processes IPC and network messages.
+    IO,
+
+    // This is the thread that interacts with the file system.
+    FILE,
+
+    // This is the thread that interacts with the database.
+    DB,
+
+    // This is the thread that interacts with the history database.
+    HISTORY,
+
+    // This identifier does not represent a thread.  Instead it counts the
+    // number of well-known threads.  Insert new well-known threads before this
+    // identifier.
+    ID_COUNT
+  };
+
+  // Construct a ChromeThread with the supplied identifier.  It is an error
+  // to construct a ChromeThread that already exists.
+  explicit ChromeThread(ID identifier);
+  virtual ~ChromeThread();
+
+  // Callable on any thread, this helper function returns a pointer to the
+  // thread's MessageLoop.
+  //
+  // WARNING:
+  //   Nothing in this class prevents the MessageLoop object returned from this
+  //   function from being destroyed on another thread.  Use with care.
+  //
+  static MessageLoop* GetMessageLoop(ID identifier);
+
+ private:
+  // The identifier of this thread.  Only one thread can exist with a given
+  // identifier at a given time.
+  ID identifier_;
+
+  // This lock protects |chrome_threads_|.  Do not read or modify that array
+  // without holding this lock.  Do not block while holding this lock.
+  static Lock lock_;
+
+  // An array of the ChromeThread objects.  This array is protected by |lock_|.
+  // The threads are not owned by this array.  Typically, the threads are owned
+  // on the IU thread by the g_browser_process object.  ChromeThreads remove
+  // themselves from this array upon destruction.
+  static ChromeThread* chrome_threads_[ID_COUNT];
+};
+
+#endif  // #ifndef CHROME_BROWSER_CHROME_THREAD_H__