Modify ThreadChecker and NonThreadSafe so that their functionality is

net/url_request/url_request_throttler_manager.h

Index: net/url_request/url_request_throttler_manager.h
diff --git a/net/url_request/url_request_throttler_manager.h b/net/url_request/url_request_throttler_manager.h
index 1862cd0622b8bc2de2acbfa0cb94d338ab744678..376e9f7df235e7f6e868fdfdcf45f68954caed72 100644
--- a/net/url_request/url_request_throttler_manager.h
+++ b/net/url_request/url_request_throttler_manager.h
@@ -11,37 +11,12 @@
 #include "base/basictypes.h"
 #include "base/scoped_ptr.h"
 #include "base/singleton.h"
-#include "base/synchronization/lock.h"  // ThreadCheckerForRelease
-#include "base/threading/platform_thread.h"  // ThreadCheckerForRelease
+#include "base/threading/thread_checker.h"
 #include "googleurl/src/gurl.h"
 #include "net/url_request/url_request_throttler_entry.h"
 
 namespace net {
 
-// TODO(joi): Delete this temporary copy of base::ThreadChecker (needed to
-// enable it in release builds) and go back to simply inheriting from
-// NonThreadSafe once crbug.com/71721 has been tracked down.
-class ThreadCheckerForRelease {
- public:
-  ThreadCheckerForRelease();
-  ~ThreadCheckerForRelease();
-
-  bool CalledOnValidThread() const;
-
-  // Changes the thread that is checked for in CalledOnValidThread.  This may
-  // be useful when an object may be created on one thread and then used
-  // exclusively on another thread.
-  void DetachFromThread();
-
- private:
-  void EnsureThreadIdAssigned() const;
-
-  mutable base::Lock lock_;
-  // This is mutable so that CalledOnValidThread can set it.
-  // It's guarded by |lock_|.
-  mutable base::PlatformThreadId valid_thread_id_;
-};
-
 // Class that registers URL request throttler entries for URLs being accessed
 // in order to supervise traffic. URL requests for HTTP contents should
 // register their URLs in this manager on each request.
@@ -53,10 +28,7 @@ class ThreadCheckerForRelease {
 // and path. All URLs converted to the same ID will share the same entry.
 //
 // NOTE: All usage of the singleton object of this class should be on the same
-// thread.
-//
-// TODO(joi): Switch back to NonThreadSafe (and remove checks in release builds)
-// once crbug.com/71721 has been tracked down.
+// thread (construction and destruction excluded).
 class URLRequestThrottlerManager {
  public:
   static URLRequestThrottlerManager* GetInstance();
@@ -141,7 +113,11 @@ class URLRequestThrottlerManager {
   // workaround.
   bool being_tested_;
 
-  ThreadCheckerForRelease thread_checker_;
+  // Check threads even in release builds.
+  //
+  // TODO(joi): Switch back to just inheriting NonThreadSafe once
+  // crbug.com/71721 has been tracked down.
+  base::ThreadCheckerImpl thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(URLRequestThrottlerManager);
 };