Removed the redundant 'OS=win' condition

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 6f62a0f4610bcaf4059ab914be9f052f51886ad7..e981f28adde5c3307bf44db41ca622c05277ee9b 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -3004,14 +3004,15 @@
                   'VCCLCompilerTool': { 'WarnAsError': 'false' },
                 }
               }],
+              [ 'component=="shared_library"', {
+              # TODO(darin): Unfortunately, some third_party code depends on base.
+                'msvs_disabled_warnings': [
+                  4251,  # class 'std::xx' needs to have dll-interface.
+                 ],
+              }],
             ],
           }],
-          # TODO(darin): Unfortunately, some third_party code depends on base.
-          [ 'OS=="win" and component=="shared_library"', {
-            'msvs_disabled_warnings': [
-              4251,  # class 'std::xx' needs to have dll-interface.
-            ],
-          }],
+
           [ 'OS=="mac" or OS=="ios"', {
             'xcode_settings': {
               'WARNING_CFLAGS!': ['-Wall', '-Wextra'],