Sync UI: Fix a typo in the sync signin flag.

BUG=none
TEST=none
TBR=csilv

Review URL: https://chromiumcodereview.appspot.com/10219005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@133764 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/about_flags.cc

@@ -644,7 +644,7 @@ const Experiment kExperiments[] = {
   },
 #endif
   {
-    "enable-sync-signing",
+    "enable-sync-signin",
     IDS_ENABLE_SYNC_SIGNIN_NAME,
     IDS_ENABLE_SYNC_SIGNIN_DESCRIPTION,
     kOsAll,