Add /Gw to the compiler command line to reduce .dll sizes by 0.85%

build/internal/release_defaults.gypi

 # 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.
 {
   'msvs_settings': {
     'VCCLCompilerTool': {
       'StringPooling': 'true',
+      'AdditionalOptions': [
+          '/Gw',  # Put data in separate COMDATs, new in VS 2013 Update 2
+      ],
     },
     'VCLinkerTool': {
       # No incremental linking.
       'LinkIncremental': '1',
       # Eliminate Unreferenced Data (/OPT:REF).
       'OptimizeReferences': '2',
       # Folding on (/OPT:ICF).
       'EnableCOMDATFolding': '2',
     },
   },
 }