Purify support:...

build/internal/release_impl_official.scons

 # Copyright (c) 2006-2008 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.
 
 __doc__ = """
 Release settings for official Chromium builds.
 """
 
 Import("env")
 
 env.ApplySConscript(['release_defaults.scons'])
 
 if env.Bit('windows'):
+  env.Replace(
+      CHROMIUM_CC_OPT_FLAGS = [
+          '/Ox',    # VCCLCompilerTool.Optimization="3"
+      ],
+  ),
   env.Append(
       ARFLAGS = [
           '/ltcg',
       ],
       CCFLAGS = [
-          '/Ox',    # VCCLCompilerTool.Optimization="3"
           '/Ob2',   # VCCLCompilerTool.InlineFunctionExpansion="2"
           '/Oi',    # VCCLCompilerTool.EnableIntrinsicFunctions="true"
           '/Os',    # VCCLCompilerTool.FavorSizeOrSpeed="2"
           '/Ox',    # VCCLCompilerTool.OmitFramePointers="true"
           '/GT',    # VCCLCompilerTool.EnableFiberSafeOptimizations="true"
           '/GL',    # VCCLCompilerTool.WholeProgramOptimization="true"
       ]
       LINKFLAGS = [
           '/LTCG',  # VCLinkerTool.LinkTimeCodeGeneration="1"
       ],
   )