Only show start/stop mirroring button when there are multiple displays.

Also, redirect the page to chrome://settings when only one monitor is
connected, so we can stop showing the dialog for now. In the future
we may decide to show the page for some reason.

BUG=169124
TEST=manually on parrot

Review URL: https://codereview.chromium.org/11818043

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@176089 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/options/chromeos/display_options.js

@@ -835,6 +835,7 @@ cr.define('options', function() {
         $('selected-display-data-container').hidden = true;
         $('display-configuration-arrow').hidden = true;
         $('display-options-set-primary').hidden = true;
+        $('display-options-toggle-mirroring').hidden = true;
         return;
       }
 
@@ -873,6 +874,8 @@ cr.define('options', function() {
 
       $('display-options-set-primary').hidden =
           this.displays_[this.focusedIndex_].isPrimary;
+      $('display-options-toggle-mirroring').hidden =
+          (this.displays_.length <= 1);
     },
 
     /**
@@ -1050,6 +1053,11 @@ cr.define('options', function() {
      * @private
      */
     onDisplayChanged_: function(mirroring, displays, layout, offset) {
+      if (displays.length <= 1) {
+        OptionsPage.showDefaultPage();
+        return;
+      }
+
       this.mirroring_ = mirroring;
       this.layout_ = layout;
       this.offset_ = offset;