base: Constantify thread_name() getter accessor.

base/threading/thread.h

 // Copyright (c) 2012 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_THREADING_THREAD_H_
 #define BASE_THREADING_THREAD_H_
 
 #include <string>
 
 #include "base/base_export.h"
@@ skipping 113 matching lines @@
   // Returns a MessageLoopProxy for this thread.  Use the MessageLoopProxy's
   // PostTask methods to execute code on the thread.  This only returns
   // non-NULL after a successful call to Start. After Stop has been called,
   // this will return NULL. Callers can hold on to this even after the thread
   // is gone.
   scoped_refptr<MessageLoopProxy> message_loop_proxy() const {
     return message_loop_ ? message_loop_->message_loop_proxy() : NULL;
   }
 
   // Returns the name of this thread (for display in debugger too).
-  const std::string &thread_name() { return name_; }
+  const std::string& thread_name() const { return name_; }
 
   // The native thread handle.
   PlatformThreadHandle thread_handle() { return thread_; }
 
   // The thread ID.
   PlatformThreadId thread_id() const { return thread_id_; }
 
   // Returns true if the thread has been started, and not yet stopped.
   bool IsRunning() const;
 
@@ skipping 59 matching lines @@
   std::string name_;
 
   friend void ThreadQuitHelper();
 
   DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_H_