Add COMPONENT_BUILD global define.

build/common.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.
 
 # 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 676 matching lines @@
           'win_debug_RuntimeLibrary%': '1',   # 1 = /MTd (debug static)
         }],
       ],
     },
     'conditions': [
       ['branding=="Chrome"', {
         'defines': ['GOOGLE_CHROME_BUILD'],
       }, {  # else: branding!="Chrome"
         'defines': ['CHROMIUM_BUILD'],
       }],
+      ['component=="shared_library"', {
+        'defines': ['COMPONENT_BUILD'],
+      }],
       ['toolkit_views==1', {
         'defines': ['TOOLKIT_VIEWS=1'],
       }],
       ['toolkit_uses_pure_views==1', {
         'defines': ['TOOLKIT_USES_PURE_VIEWS=1'],
       }],
       ['views_compositor==1', {
         'defines': ['VIEWS_COMPOSITOR=1'],
       }],
       ['chromeos==1', {
@@ skipping 208 matching lines @@
           # We use "POSIX" to refer to all non-Windows operating systems.
           ['OS=="win"', {
             'sources/': [ ['exclude', '_posix\\.(h|cc)$'] ],
             # turn on warnings for signed/unsigned mismatch on chromium code.
             'msvs_settings': {
               'VCCLCompilerTool': {
                 'AdditionalOptions': ['/we4389'],
               },
             },
           }],
+          ['OS=="win" and component=="shared_library"', {
+            'msvs_disabled_warnings': [
+              4251,  # class 'std::xx' needs to have dll-interface.
+            ],
+          }],
           ['chromeos!=1', {
             'sources/': [ ['exclude', '_chromeos\\.(h|cc)$'] ]
           }],
           ['toolkit_views==0', {
             'sources/': [ ['exclude', '_views\\.(h|cc)$'] ]
           }],
         ],
       }],
     ],  # target_conditions for 'target_defaults'
     'default_configuration': 'Debug',
@@ skipping 901 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',
   },
 }