Remove ThreadRestrictions::ScopedAllowSingleton.

base/threading/thread_restrictions.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_RESTRICTIONS_H_
 #define BASE_THREADING_THREAD_RESTRICTIONS_H_
 
 #include "base/base_export.h"
 #include "base/logging.h"
 #include "base/macros.h"
@@ skipping 117 matching lines @@
    public:
     ScopedAllowIO() { previous_value_ = SetIOAllowed(true); }
     ~ScopedAllowIO() { SetIOAllowed(previous_value_); }
    private:
     // Whether IO is allowed when the ScopedAllowIO was constructed.
     bool previous_value_;
 
     DISALLOW_COPY_AND_ASSIGN(ScopedAllowIO);
   };
 
-  // Constructing a ScopedAllowSingleton temporarily allows accessing for the
-  // current thread.  Doing this is almost always incorrect.
-  class BASE_EXPORT ScopedAllowSingleton {
-   public:
-    ScopedAllowSingleton() { previous_value_ = SetSingletonAllowed(true); }
-    ~ScopedAllowSingleton() { SetSingletonAllowed(previous_value_); }
-   private:
-    // Whether singleton use is allowed when the ScopedAllowSingleton was
-    // constructed.
-    bool previous_value_;
-
-    DISALLOW_COPY_AND_ASSIGN(ScopedAllowSingleton);
-  };
-
 #if DCHECK_IS_ON()
   // Set whether the current thread to make IO calls.
   // Threads start out in the *allowed* state.
   // Returns the previous value.
   static bool SetIOAllowed(bool allowed);
 
   // Check whether the current thread is allowed to make IO calls,
   // and DCHECK if not.  See the block comment above the class for
   // a discussion of where to add these checks.
   static void AssertIOAllowed();
@@ skipping 98 matching lines @@
 
     DISALLOW_COPY_AND_ASSIGN(ScopedAllowWait);
   };
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_RESTRICTIONS_H_