Make codesighs build on Win64

BUG=166496
BUG=167187
TBR=scottmg


Review URL: https://chromiumcodereview.appspot.com/11887007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@176594 0039d316-1c4b-4281-b951-d872f2087c98

third_party/codesighs/codesighs.gyp

@@ -3,6 +3,10 @@
 # found in the LICENSE file.
 
 {
+  'target_defaults': {
+      # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+      'msvs_disabled_warnings': [ 4267, ],
+  },
   'targets': [
     {
       'target_name': 'codesighs',