Implement initial chrome.browserAction.openPopup API.

chrome/common/extensions/api/_api_features.json

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // 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.
 
 {
   "activityLogPrivate": {
     "dependencies": ["permission:activityLogPrivate"],
@@ skipping 84 matching lines @@
   "bookmarks.import": {
     "extension_types": ["extension"],
     "location": "component"
   },
   "brailleDisplayPrivate": {
     "dependencies": ["permission:brailleDisplayPrivate"],
     "contexts": ["blessed_extension"]
   },
   "browserAction": {
     "dependencies": ["manifest:browser_action"],
+    "contexts": ["blessed_extension", "unblessed_extension"]
+  },
+  // The following API enabled for dev pending resolution of security concerns.
+  // It is enabled for stable only for whitelisted extensions.
+  "browserAction.openPopup": [{
+    "channel": "dev",
+    "dependencies": ["manifest:browser_action"],
     "contexts": ["blessed_extension"]
-  },
+  }, {
+    "channel": "stable",
+    "dependencies": ["manifest:browser_action"],
+    "whitelist": [
+      "enhhojjnijigcajfphajepfemndkmdlo",  // Dev
+      "pkedcjkdefgpdelpbcmbmeomcjbeemfm",  // Trusted Tester
+      "fmfcbgogabcbclcofgocippekhfcmgfj",  // Staging
+      "hfaagokkkhdbgiakmmlclaapfelnkoah",  // Canary
+      "F155646B5D1CA545F7E1E4E20D573DFDD44C2540",  // Trusted Tester (public)
+      "16CA7A47AAE4BE49B1E75A6B960C3875E945B264"   // Release
+    ],
+    "contexts": ["blessed_extension"]
+  }],
   "browsingData": {
     "dependencies": ["permission:browsingData"],
     "contexts": ["blessed_extension"]
   },
   "cast.channel": {
     "dependencies": ["permission:cast"],
     "contexts": ["blessed_extension"]
   },
   "chromeosInfoPrivate": {
     "platforms": ["chromeos"],
@@ skipping 555 matching lines @@
     "internal": true,
     "channel": "stable",
     "dependencies": ["permission:webview"],
     "contexts": ["blessed_extension"]
   },
   "windows": {
     "dependencies": ["api:tabs"],
     "contexts": ["blessed_extension"]
   }
 }