Make webkit_glue build on Win64

Just c4267 build suppressions. 

BUG=166496
BUG=167187
R=brettw@chromium.org
TBR=brettw@chromium.org
Review URL: https://codereview.chromium.org/12084104

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@180142 0039d316-1c4b-4281-b951-d872f2087c98

webkit/glue/webkit_glue.gypi

@@ -463,7 +463,8 @@
           'sources!': [
             'plugins/plugin_stubs.cc',
           ],
-          'msvs_disabled_warnings': [ 4800 ],
+          # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+          'msvs_disabled_warnings': [ 4800, 4267 ],
           'conditions': [
             ['inside_chromium_build==1 and component=="shared_library"', {
               'dependencies': [