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

base/debug/debugger.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 is a cross platform interface for helper functions related to
 // debuggers.  You should use this to test if you're running under a debugger,
 // and if you would like to yield (breakpoint) into the debugger.
 
 #ifndef BASE_DEBUG_DEBUGGER_H
 #define BASE_DEBUG_DEBUGGER_H
-#pragma once
 
 #include "base/base_export.h"
 
 namespace base {
 namespace debug {
 
 // Starts the registered system-wide JIT debugger to attach it to specified
 // process.
 BASE_EXPORT bool SpawnDebuggerOnProcess(unsigned process_id);
 
@@ skipping 18 matching lines @@
 // release mode doesn't do this stuff --  this is controlled separately).
 // Normally UI is not suppressed.  This is normally used when running automated
 // tests where we want a crash rather than a dialog or a debugger.
 BASE_EXPORT void SetSuppressDebugUI(bool suppress);
 BASE_EXPORT bool IsDebugUISuppressed();
 
 }  // namespace debug
 }  // namespace base
 
 #endif  // BASE_DEBUG_DEBUGGER_H