Fix display of gaia buttons in add account flow

Add enableGaiaActionButtons_ parameter to shouldShowGaiaButtons_ call,
to update "hidden" property of the buttons when the flag is updated.

Bug: b/177064517
Change-Id: I46999193c2d7f42485b15053f9eff22964becb93
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2620799
Commit-Queue: Anastasiia N <anastasiian@chromium.org>
Reviewed-by: Kush Sinha <sinhak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842017}

chrome/browser/resources/inline_login/inline_login_app.html

@@ -93,7 +93,8 @@
     </cr-button>
 
     <div class="action-buttons"
-        hidden$="[[!shouldShowGaiaButtons_(currentView_)]]">
+        hidden$="[[!shouldShowGaiaButtons_(enableGaiaActionButtons_,
+                                           currentView_)]]">
       <gaia-action-buttons authenticator="[[authExtHost_]]">
       </gaia-action-buttons>
     </div>

chrome/browser/resources/inline_login/inline_login_app.js

@@ -111,7 +111,10 @@ Polymer({
    */
   isLoginPrimaryAccount_: false,
 
-  /** @private {boolean} */
+  /**
+   * TODO(crbug.com/1164862): cleanup this flag, since it's enabled by default.
+   * @private {boolean}
+   */
   enableGaiaActionButtons_: false,
 
   /** @override */