ChromeOS OOBE: Implement network selection screen "Back" button.

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

Index: chrome/browser/resources/chromeos/login/oobe_welcome.js
diff --git a/chrome/browser/resources/chromeos/login/oobe_welcome.js b/chrome/browser/resources/chromeos/login/oobe_welcome.js
index da6a134fed61ad7e274e6f45ea85801a03cd61ff..db32a89e4c7f1f5adcc999f26544c8c0ab21f59b 100644
--- a/chrome/browser/resources/chromeos/login/oobe_welcome.js
+++ b/chrome/browser/resources/chromeos/login/oobe_welcome.js
@@ -123,21 +123,21 @@ Polymer({
     return [
       {
         customItemName: 'proxySettingsMenuName',
-        polymerIcon: 'oobe-welcome:add',
+        polymerIcon: 'oobe-welcome-20:add-proxy',
         customData: {
           onTap: function() { self.OpenProxySettingsDialog_(); },
         },
       },
       {
         customItemName: 'addWiFiNetworkMenuName',
-        polymerIcon: 'oobe-welcome:add',
+        polymerIcon: 'oobe-welcome-20:add-wifi',
         customData: {
           onTap: function() { self.OpenAddWiFiNetworkDialog_(); },
         },
       },
       {
         customItemName: 'addMobileNetworkMenuName',
-        polymerIcon: 'oobe-welcome:add',
+        polymerIcon: 'oobe-welcome-20:add-cellular',
         customData: {
           onTap: function() { self.OpenAddWiFiNetworkDialog_(); },
         },
@@ -277,6 +277,17 @@ Polymer({
   },
 
   /**
+   * Handle "<- Back" button on network selection screen.
+   *
+   * @private
+   */
+  onNetworkSelectionBackButtonPressed_: function() {
+    this.networkLastSelectedGuid_ = '';
+    this.hideAllScreens_();
+    this.welcomeScreenShown = true;
+  },
+
+  /**
    * Handle language selection.
    *
    * @param {!{detail: {!OobeTypes.LanguageDsc}}} event