Enable webview tag in webui

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.
 
 // This features file defines extension APIs implemented under src/chrome.
 // See extensions/common/features/* to understand this file, in particular
 // feature.h, simple_feature.h, and base_feature_provider.h.
 //
 // Note that specifying "web_page", "blessed_web_page", or "all" as a context
 // type will require manually updating chrome/renderer/resources/dispatcher.cc.
@@ skipping 175 matching lines @@
     "contexts": ["blessed_extension"]
   },
   "cast.streaming.udpTransport": {
     "dependencies": ["permission:cast.streaming"],
     "contexts": ["blessed_extension"]
   },
   "chromeosInfoPrivate": {
     "dependencies": ["permission:chromeosInfoPrivate"],
     "contexts": ["blessed_extension"]
   },
-  "chromeWebViewInternal": {
+  "chromeWebViewInternal": [{
     "internal": true,
     "dependencies": ["permission:webview"],
     "contexts": ["blessed_extension"]
-  },
+  }, {
+    "internal": true,
+    "channel": "dev",
+    "contexts": ["webui"],
+    "matches": ["chrome://chrome-signin/*"]
+  }],
   "cloudPrintPrivate": {
     "dependencies": ["permission:cloudPrintPrivate"],
     "contexts": ["blessed_extension"]
   },
   "commandLinePrivate": {
     "dependencies": ["permission:commandLinePrivate"],
     "contexts": ["blessed_extension"]
   },
   "commands": {
     "dependencies": ["manifest:commands"],
@@ skipping 513 matching lines @@
     "contexts": ["blessed_extension"]
   },
   "webRequestInternal": [{
     "internal": true,
     "channel": "stable",
     "contexts": ["blessed_extension"]
   }, {
     // webview uses webRequestInternal API.
     "channel": "stable",
     "internal": true,
-    "dependencies": ["permission:webview"],

[Ken Rockot(use gerrit already), 2014/09/22 20:47:32]

Why are you replacing this feature instead of just adding another entry to
webRequestInternal?

[guohui, 2014/09/22 20:58:58]

because i added this feature for some old code that has been removed, and will
be replaced by a pure webui-based implementation.

-    "contexts": ["unblessed_extension"]
+    "contexts": ["webui"],
+    "matches": ["chrome://chrome-signin/*"]
   }],
   "webrtcAudioPrivate": {
     "dependencies": ["permission:webrtcAudioPrivate"],
     "contexts": ["blessed_extension"]
   },
   "webrtcLoggingPrivate": {
     "dependencies": ["permission:webrtcLoggingPrivate"],
     "contexts": ["blessed_extension"]
   },
   "webstore": {
@@ skipping 12 matching lines @@
     "dependencies": ["permission:webstorePrivate"],
     // NOTE: even though this is only used by the webstore hosted app, which
     // normally would mean blessed_web_page, component hosted apps are actually
     // given the blessed_extension denomination. Confusing.
     "contexts": ["blessed_extension"]
   },
   "webViewRequest": [{
     "dependencies": ["permission:webview"],
     "contexts": ["blessed_extension"]
   }, {
-    // Component extensions can use the webViewRequest API from iframes.

[Ken Rockot(use gerrit already), 2014/09/22 20:47:32]

Same question - why are you replacing an existing feature?

[guohui, 2014/09/22 20:58:58]

same as above.

-    "location": "component",
-    "dependencies": ["permission:webview"],
-    "contexts": ["unblessed_extension"]
+    "channel": "stable",
+    "contexts": ["webui"],
+    "matches": ["chrome://chrome-signin/*"]
   }],
   "webviewTag": {
     "internal": true,
     "channel": "stable",
     "dependencies": ["permission:webview"],
     "contexts": ["blessed_extension"]
   },
   "windows": {
     "dependencies": ["api:tabs"],
     "contexts": ["blessed_extension"]
   }
 }