Make the Visual Studio /MP flag configurable.

build/common.gypi

 # Copyright (c) 2009 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.
 
 {
   'variables': {
     # .gyp files should set chromium_code to 1 if they build Chromium-specific
     # code, as opposed to external code.  This variable is used to control
     # such things as the set of warnings to enable, and whether warnings are
     # treated as errors.
@@ skipping 54 matching lines @@
     # Yes(1) means set use the common linker options.        
     'msvs_use_common_linker_extras%': 1,
 
     # TODO(sgk): eliminate this if possible.
     # It would be nicer to support this via a setting in 'target_defaults'
     # in chrome/app/locales/locales.gypi overriding the setting in the
     # 'Debug' configuration in the 'target_defaults' dict below,
     # but that doesn't work as we'd like.
     'msvs_debug_link_incremental%': '2',
 
+    # Whether to use multiple cores to compile with visual studio. This is
+    # optional because it sometimes causes corruption on VS 2005.
+    'msvs_multi_core_compile%': '',
+
     # The architecture that we're building on.
     'target_arch%': 'ia32',
 
     # By default linux does not use views. To turn on views in Linux
     # set the variable GYP_DEFINES to "toolkit_views=1", or modify
     # ~/.gyp/include.gypi .
     'toolkit_views%': 0,
 
     'chromeos%': 0,
 
@@ skipping 428 matching lines @@
         'msvs_settings': {
           'VCCLCompilerTool': {
             'MinimalRebuild': 'false',
             'ExceptionHandling': '0',
             'BufferSecurityCheck': 'true',
             'EnableFunctionLevelLinking': 'true',
             'RuntimeTypeInfo': 'false',
             'WarningLevel': '3',
             'WarnAsError': 'true',
             'DebugInformationFormat': '3',
+            'conditions': [
+              [ 'msvs_multi_core_compile',
+                {'AdditionalOptions': '/MP'}, ],
+            ],
           },
           'VCLibrarianTool': {
             'AdditionalOptions': '/ignore:4221',
             'AdditionalLibraryDirectories':
               ['<(DEPTH)/third_party/platformsdk_win2008_6_1/files/Lib'],
           },
           'VCLinkerTool': {
             'AdditionalDependencies': [
               'wininet.lib',
               'version.lib',
@@ skipping 76 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',
   },
 }