Remove #pragma once. Just from base/ for now.

base/bind_helpers.h

 // Copyright (c) 2011 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.
 
 // This defines a set of argument wrappers and related factory methods that
 // can be used specify the refcounting and reference semantics of arguments
 // that are bound by the Bind() function in base/bind.h.
 //
 // It also defines a set of simple functions and utilities that people want
 // when using Callback<> and Bind().
@@ skipping 128 matching lines @@
 //                        pointer when invoked. Only use this when necessary.
 //                        In most cases MessageLoop::DeleteSoon() is a better
 //                        fit.
 //   ScopedClosureRunner - Scoper object that runs the wrapped closure when it
 //                         goes out of scope. It's conceptually similar to
 //                         scoped_ptr<> but calls Run() instead of deleting
 //                         the pointer.
 
 #ifndef BASE_BIND_HELPERS_H_
 #define BASE_BIND_HELPERS_H_
-#pragma once
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
 #include "base/template_util.h"
 
 namespace base {
 namespace internal {
 
 // Use the Substitution Failure Is Not An Error (SFINAE) trick to inspect T
@@ skipping 394 matching lines @@
 
  private:
   Closure closure_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ScopedClosureRunner);
 };
 
 }  // namespace base
 
 #endif  // BASE_BIND_HELPERS_H_