[cros,login] Pre-load login extension in the background.

chrome/browser/resources/chromeos/login/screen_gaia_signin.js

Index: chrome/browser/resources/chromeos/login/screen_gaia_signin.js
diff --git a/chrome/browser/resources/chromeos/login/screen_gaia_signin.js b/chrome/browser/resources/chromeos/login/screen_gaia_signin.js
index ada6dde35b26f97b3ad7c21f6e4172eaecb0f007..a8c9d11017acec92cf7e083177151db52662fdc0 100644
--- a/chrome/browser/resources/chromeos/login/screen_gaia_signin.js
+++ b/chrome/browser/resources/chromeos/login/screen_gaia_signin.js
@@ -98,8 +98,18 @@ cr.define('login', function() {
      *        page.
      */
     onBeforeShow: function(data) {
-      console.log('Opening extension: ' + data.startUrl +
-                  ', opt_email=' + data.email);
+      // Announce the name of the screen, if accessibility is on.
+      $('gaia-signin-aria-label').setAttribute(
+          'aria-label', localStrings.getString('signinScreenTitle'));
+
+      // Button header is always visible when sign in is presented.
+      // Header is hidden once GAIA reports on successful sign in.
+      Oobe.getInstance().headerHidden = false;
+    },
+
+    setExtensionUrl_: function(data) {
+      $('createAccount').hidden = !data.createAccount;
+      $('guestSignin').hidden = !data.guestSignin;
 
       var params = [];
       if (data.gaiaOrigin)
@@ -117,22 +127,20 @@ cr.define('login', function() {
       if (params.length)
         url += '?' + params.join('&');
 
-      $('signin-frame').src = url;
-      this.extension_url_ = url;
+      if (data.forceReload || this.extension_url_ != url) {
+        console.log('Opening extension: ' + data.startUrl +
+                    ', opt_email=' + data.email);
 
-      $('createAccount').hidden = !data.createAccount;
-      $('guestSignin').hidden = !data.guestSignin;
+        $('signin-frame').src = url;
+        this.extension_url_ = url;
 
-      // Announce the name of the screen, if accessibility is on.
-      $('gaia-signin-aria-label').setAttribute(
-          'aria-label', localStrings.getString('signinScreenTitle'));
-
-      // Button header is always visible when sign in is presented.
-      // Header is hidden once GAIA reports on successful sign in.
-      Oobe.getInstance().headerHidden = false;
-
-      this.loading = true;
-      this.clearRetry_();
+        this.loading = true;
+        this.clearRetry_();
+      } else if (!this.loading) {

[xiyuan, 2011/11/03 16:52:33]

When will the two "else" branch below get hit?

It seems a bit strange to me that a SetExtensionUrl call triggers
"loginWebuiRead".

[altimofeev, 2011/11/03 17:22:32]

* "!this.loading": first click on 'Add new user' button, after extension has
been loaded in background.
* "this.loading": first click on 'Add new user' button, loading is in progress
(probably, network error). So we try to load again.

Do you think I should change SetExtensionUrl to something which implicitly says
that this URL will also be fetched? What about 'StartExtensionLoading'?

[xiyuan, 2011/11/03 17:36:04]

In this case, if Gaia is loaded successfully, "loginWebuiRead" should be fired
already in onMessage handler and we don't need to fire it again here.
Okay. We probably need this to show proper error message.
Think a name implies loading is better. I prefer to call it "LoadExtension" or
"LoadAuthExt" etc.

[altimofeev, 2011/11/07 16:21:59]

Done - moved the logic fully to the C++ part.
Done.

+        chrome.send('loginWebuiReady');
+      } else {
+        this.doReload();
+      }
     },
 
     /**
@@ -215,6 +223,10 @@ cr.define('login', function() {
     }
   };
 
+  GaiaSigninScreen.setExtensionUrl = function(data) {
+    $('gaia-signin').setExtensionUrl_(data);
+  };
+
   return {
     GaiaSigninScreen: GaiaSigninScreen
   };