[Extensions] Improve app custom bindings

chrome/renderer/resources/extensions/app_custom_bindings.js

Index: chrome/renderer/resources/extensions/app_custom_bindings.js
diff --git a/chrome/renderer/resources/extensions/app_custom_bindings.js b/chrome/renderer/resources/extensions/app_custom_bindings.js
index 4d58054b989b2a6b18d6ff555db9153abf1fe7c9..f1f4e5caa173035288732023dde67dc410092d8b 100644
--- a/chrome/renderer/resources/extensions/app_custom_bindings.js
+++ b/chrome/renderer/resources/extensions/app_custom_bindings.js
@@ -35,13 +35,21 @@ var app = {
 //
 // So, define it manually, and let the getIsInstalled function act as its
 // documentation.
-app.__defineGetter__('isInstalled', wrapForLogging(appNatives.GetIsInstalled));
+var isInstalled = wrapForLogging(appNatives.GetIsInstalled);
+$Object.defineProperty(
+    app, 'isInstalled',
+    {
+      __proto__: null,
+      configurable: true,
+      enumerable: true,
+      get: function() { return isInstalled(); },
+    });
 
 // Called by app_bindings.cc.
 function onInstallStateResponse(state, callbackId) {
   var callback = callbacks[callbackId];
   delete callbacks[callbackId];
-  if (typeof(callback) == 'function') {
+  if (typeof callback == 'function') {
     try {
       callback(state);
     } catch (e) {
@@ -52,16 +60,24 @@ function onInstallStateResponse(state, callbackId) {
 }
 
 // TODO(kalman): move this stuff to its own custom bindings.
-var callbacks = {};
+var callbacks = { __proto__: null };
 var nextCallbackId = 1;
 
-app.installState = function getInstallState(callback) {
+function getInstallState(callback) {
   var callbackId = nextCallbackId++;
   callbacks[callbackId] = callback;
   appNatives.GetInstallState(callbackId);
-};
-if (extensionId)
-  app.installState = wrapForLogging(app.installState);
+}
+
+var installState = wrapForLogging(getInstallState);
+$Object.defineProperty(
+    app, 'installState',
+    {
+      __proto__: null,
+      configurable: true,
+      enumerable: true,
+      get: function() { return installState; },

[jbroman, 2017/05/08 14:25:25]

This makes it an accessor property as opposed to a data property. Intentional?
I'd have expected:

$Object.defineProperty(
    app, 'installState',
    {
      __proto__: null,
      configurable: true,
      enumerable: true,
      // possibly also "writable: true" if you want to mimic the kind of
property app.installState ordinarily creates
      value: installState
    });

(Doesn't apply above, because you are replacing an accessor property there.)

[Devlin, 2017/05/11 14:30:38]

Done.

+    });
 
 exports.$set('binding', app);
 exports.$set('onInstallStateResponse', onInstallStateResponse);