ChromeOS: Fix layout when Gaia containers are updated.

This CL updates Gaia containers size after its state has been updated, not
before.

Bug: 745933
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I1517fe77e1148f6af27e816782767f9b5ee22d77
Reviewed-on: https://chromium-review.googlesource.com/578869Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Alexander Alekseev <alemate@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488387}

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

@@ -345,7 +345,6 @@ login.createScreen('GaiaSigninScreen', 'gaia-signin', function() {
      */
     set screenMode(value) {
       this.screenMode_ = value;
-      this.updateSigninFrameContainers_();
       switch (this.screenMode_) {
         case ScreenMode.DEFAULT:
           $('signin-frame-dialog').hidden = false;
@@ -376,6 +375,7 @@ login.createScreen('GaiaSigninScreen', 'gaia-signin', function() {
           $('offline-ad-auth').hidden = true;
           break;
       }
+      this.updateSigninFrameContainers_();
       chrome.send('updateOfflineLogin', [this.isOffline()]);
       this.updateControlsState();
     },