Fixed a runtime error caused by incomplete manifestTypes in _api_features.json

BUG=302841
R=kalman@chromium.org

Review URL: https://codereview.chromium.org/25650002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226498 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/extensions/api/_api_features.json

@@ -336,7 +336,7 @@
   "manifestTypes": {
     "internal": true,
     "channel": "stable",
-    "contexts": "all"
+    "contexts": ["blessed_extension"]
   },
   "mediaGalleries": {
     "dependencies": ["permission:mediaGalleries"],