Only use /Gw in non-ASan builds on Windows

build/common.gypi

 # 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 3354 matching lines @@
               }],
               ['win_release_OmitFramePointers==0', {
                 'OmitFramePointers': 'false',
                 # The above is not sufficient (http://crbug.com/106711): it
                 # simply eliminates an explicit "/Oy", but both /O2 and /Ox
                 # perform FPO regardless, so we must explicitly disable.
                 # We still want the false setting above to avoid having
                 # "/Oy /Oy-" and warnings about overriding.
                 'AdditionalOptions': ['/Oy-'],
               }],
+              ['asan==0', {
+                # Put data in separate COMDATs. This allows the linker
+                # to put bit-identical constants at the same address even if
+                # they're unrelated constants, which saves binary size.
+                # This optimization can't be used when ASan is enabled because
+                # it is not compatible with the ASan ODR checker.
+                'AdditionalOptions': ['/Gw'],
+              }],
             ],
             'AdditionalOptions': [
                 '/d2Zi+',  # Improve debugging of Release builds.
                 '/Zc:inline',  # Remove unreferenced COMDAT (faster links).
-                '/Gw',  # Put data in separate COMDATs.
                 '<@(win_release_extra_cflags)',
             ],
           },
           'VCLinkerTool': {
             # LinkIncremental is a tri-state boolean, where 0 means default
             # (i.e., inherit from parent solution), 1 means false, and
             # 2 means true.
             'LinkIncremental': '1',
             # This corresponds to the /PROFILE flag which ensures the PDB
             # file contains FIXUP information (growing the PDB file by about
@@ skipping 2430 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }