Revert "Add COMPONENT_BUILD global define. "

The change broke compilation on Linux Builder (dbg)(shared):
http://build.chromium.org/p/chromium/builders/Linux%20Builder%20%28dbg%29%28shared%29/builds/3365/steps/compile/logs/stdio

TBR=darin
BUG=None
TEST=None

Review URL: http://codereview.chromium.org/7352014

git-svn-id: http://src.chromium.org/svn/trunk/src/build@92329 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -694,9 +694,6 @@
       }, {  # else: branding!="Chrome"
         'defines': ['CHROMIUM_BUILD'],
       }],
-      ['component=="shared_library"', {
-        'defines': ['COMPONENT_BUILD'],
-      }],
       ['toolkit_views==1', {
         'defines': ['TOOLKIT_VIEWS=1'],
       }],
@@ -925,11 +922,6 @@
               },
             },
           }],
-          ['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)$'] ]
           }],