diff -r 000000000000 -r 6474c204b198 browser/devtools/app-manager/content/manifest-editor.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/app-manager/content/manifest-editor.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,146 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+Cu.import("resource://gre/modules/osfile.jsm");
+const {VariablesView} =
+  Cu.import("resource:///modules/devtools/VariablesView.jsm", {});
+
+const VARIABLES_VIEW_URL =
+  "chrome://browser/content/devtools/widgets/VariablesView.xul";
+
+function ManifestEditor(project) {
+  this.project = project;
+  this._onContainerReady = this._onContainerReady.bind(this);
+  this._onEval = this._onEval.bind(this);
+  this._onSwitch = this._onSwitch.bind(this);
+  this._onDelete = this._onDelete.bind(this);
+  this._onNew = this._onNew.bind(this);
+}
+
+ManifestEditor.prototype = {
+  get manifest() { return this.project.manifest; },
+
+  get editable() { return this.project.type == "packaged"; },
+
+  show: function(containerElement) {
+    let deferred = promise.defer();
+    let iframe = this._iframe = document.createElement("iframe");
+
+    iframe.addEventListener("load", function onIframeLoad() {
+      iframe.removeEventListener("load", onIframeLoad, true);
+      deferred.resolve(iframe.contentWindow);
+    }, true);
+
+    iframe.setAttribute("src", VARIABLES_VIEW_URL);
+    iframe.classList.add("variables-view");
+    containerElement.appendChild(iframe);
+
+    return deferred.promise.then(this._onContainerReady);
+  },
+
+  _onContainerReady: function(varWindow) {
+    let variablesContainer = varWindow.document.querySelector("#variables");
+
+    variablesContainer.classList.add("manifest-editor");
+
+    let editor = this.editor = new VariablesView(variablesContainer);
+
+    editor.onlyEnumVisible = true;
+    editor.alignedValues = true;
+    editor.actionsFirst = true;
+
+    if (this.editable) {
+      editor.eval = this._onEval;
+      editor.switch = this._onSwitch;
+      editor.delete = this._onDelete;
+      editor.new = this._onNew;
+    }
+
+    return this.update();
+  },
+
+  _onEval: function(variable, value) {
+    let parent = this._descend(variable.ownerView.symbolicPath);
+    try {
+      parent[variable.name] = JSON.parse(value);
+    } catch(e) {
+      Cu.reportError(e);
+    }
+
+    this.update();
+  },
+
+  _onSwitch: function(variable, newName) {
+    if (variable.name == newName) {
+      return;
+    }
+
+    let parent = this._descend(variable.ownerView.symbolicPath);
+    parent[newName] = parent[variable.name];
+    delete parent[variable.name];
+
+    this.update();
+  },
+
+  _onDelete: function(variable) {
+    let parent = this._descend(variable.ownerView.symbolicPath);
+    delete parent[variable.name];
+  },
+
+  _onNew: function(variable, newName, newValue) {
+    let parent = this._descend(variable.symbolicPath);
+    try {
+      parent[newName] = JSON.parse(newValue);
+    } catch(e) {
+      Cu.reportError(e);
+    }
+
+    this.update();
+  },
+
+  /**
+   * Returns the value located at a given path in the manifest.
+   * @param path array
+   *        A string for each path component: ["developer", "name"]
+   */
+  _descend: function(path) {
+    let parent = this.manifest;
+    while (path.length) {
+      parent = parent[path.shift()];
+    }
+    return parent;
+  },
+
+  update: function() {
+    this.editor.rawObject = this.manifest;
+    this.editor.commitHierarchy();
+
+    // Wait until the animation from commitHierarchy has completed
+    let deferred = promise.defer();
+    setTimeout(deferred.resolve, this.editor.lazyEmptyDelay + 1);
+    return deferred.promise;
+  },
+
+  save: function() {
+    if (this.editable) {
+      let validator = new AppValidator(this.project);
+      let manifestFile = validator._getPackagedManifestFile();
+      let path = manifestFile.path;
+
+      let encoder = new TextEncoder();
+      let data = encoder.encode(JSON.stringify(this.manifest, null, 2));
+
+      return OS.File.writeAtomic(path, data, { tmpPath: path + ".tmp" });
+    }
+
+    return promise.resolve();
+  },
+
+  destroy: function() {
+    if (this._iframe) {
+      this._iframe.remove();
+    }
+  }
+};