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

base/stack_container.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_STACK_CONTAINER_H_
 #define BASE_STACK_CONTAINER_H_
-#pragma once
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "build/build_config.h"
 #include "base/memory/aligned_memory.h"
 
 // This allocator can be used with STL containers to provide a stack buffer
 // from which to allocate memory and overflows onto the heap. This stack buffer
@@ skipping 225 matching lines @@
 
   // Vectors are commonly indexed, which isn't very convenient even with
   // operator-> (using "->at()" does exception stuff we don't want).
   T& operator[](size_t i) { return this->container().operator[](i); }
   const T& operator[](size_t i) const {
     return this->container().operator[](i);
   }
 };
 
 #endif  // BASE_STACK_CONTAINER_H_