Allow component IME extension use app.window and add 'ime' window type for app window

extensions/common/api/_api_features.json

 // Copyright 2014 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/extensions.
 // 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 18 matching lines @@
     "component_extensions_auto_granted": false,
     "contexts": ["blessed_extension"],
     "extension_types": ["extension"],
     "noparent": true,
     "whitelist": [
       "2FC374607C2DF285634B67C64A2E356C607091C3",  // Quickoffice
       "3727DD3E564B6055387425027AD74C58784ACC15",  // Quickoffice internal
       "12E618C3C6E97495AAECF2AC12DEB082353241C6"   // QO component extension
     ]
   }],
-  "app.window": {
+  "app.window": [{
     "channel": "stable",
     "contexts": ["blessed_extension"],
     "extension_types": ["platform_app"],
     "noparent": true
-  },
-  "app.window.canSetVisibleOnAllWorkspaces": {
+  }, {
+    "channel": "stable",
+    "contexts": ["blessed_extension"],
+    "extension_types": ["extension"],
+    "noparent": true,
+    "component_extensions_auto_granted": false,
+    "whitelist": [
+      "06BE211D5F014BAB34BC22D9DDA09C63A81D828E",  // Official xkb extension
+      "F94EE6AB36D6C6588670B2B01EB65212D9C64E33"   // Open source xkb extension
+    ]
+  }],
+  // This does not need to be a complex feature if we could set "noparent" here.
+  // But set "noparent" makes this feature available on stable channel. The
+  // issue is tracked in crbug.com/415750.
+  "app.window.canSetVisibleOnAllWorkspaces": [{
+    "contexts": ["blessed_extension"],
     "channel": "dev"
-  },
+  }],
   "app.currentWindowInternal": {
     "noparent": true,
     "internal": true,
     "channel": "stable",
     "contexts": ["blessed_extension"]
   },
   "app.currentWindowInternal.setShape": {
     "dependencies": ["permission:app.window.shape"],
     "contexts": ["blessed_extension"]
   },
@@ skipping 191 matching lines @@
     "internal": true,
     "dependencies": ["permission:webview"],
     "contexts": ["blessed_extension"]
   }, {
     "internal": true,
     "channel": "dev",
     "contexts": ["webui"],
     "matches": ["chrome://chrome-signin/*"]
   }]
 }