Add variations target to translate component in gyp.

In order to build translate_core_browser from projects built
with gyp, variations is needed as a dependency.

BUG=

Review-Url: https://codereview.chromium.org/2115453004
Cr-Commit-Position: refs/heads/master@{#403363}

components/translate.gypi

@@ -22,6 +22,7 @@
         'language_usage_metrics',
         'pref_registry',
         'translate_core_common',
+        'variations',
       ],
       'include_dirs': [
         '..',