Enable _FORTIFY_SOURCE=2 with clang (unless sanitizers are used).

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 3195 matching lines @@
               'MEMORY_TOOL_REPLACES_ALLOCATOR',
               'DYNAMIC_ANNOTATIONS_ENABLED=1',
               'WTF_USE_DYNAMIC_ANNOTATIONS=1',
             ],
           }],
           ['win_use_allocator_shim==0', {
             'defines': ['NO_TCMALLOC'],
           }],
           # _FORTIFY_SOURCE isn't really supported by Clang now, see
           # http://llvm.org/bugs/show_bug.cgi?id=16821.
-          # TODO(glider): once the bug is fixed, disable source fortification
-          # under the sanitizer tools only.
-          ['os_posix==1 and (OS!="linux" or clang!=1)', {
+          # It seems to work fine with Ubuntu 12 headers though, so use it
+          # in official builds.
+          ['os_posix==1 and (asan!=1 and msan!=1 and tsan!=1 and lsan!=1 and ubsan!=1) and (OS!="linux" or clang!=1 or buildtype=="Official")', {
             'target_conditions': [
               ['chromium_code==1', {
                 # Non-chromium code is not guaranteed to compile cleanly
                 # with _FORTIFY_SOURCE. Also, fortified build may fail
                 # when optimizations are disabled, so only do that for Release
                 # build.
                 'defines': [
                   '_FORTIFY_SOURCE=2',
                 ],
               }],
@@ skipping 2275 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',
   },
 }