Implement externally_connectable! Web pages can now communicate directly with

chrome/common/extensions/api/_manifest_features.json

Index: chrome/common/extensions/api/_manifest_features.json
diff --git a/chrome/common/extensions/api/_manifest_features.json b/chrome/common/extensions/api/_manifest_features.json
index c336303ca30cc8f04a6a9acda365a3dbed5630c3..4512c5616617dd68c5639f7a4ea432d89158c8ab 100644
--- a/chrome/common/extensions/api/_manifest_features.json
+++ b/chrome/common/extensions/api/_manifest_features.json
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// See c/c/e/features/* to understand this file, in particular feature.h,
+// simple_feature.h, and base_feature_provider.h.
+
 {
   "app": {
     "channel": "stable",