Only enable mirroring for 2 displays

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

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.exportPath('options');
 
 /**
  * Enumeration of multi display mode. These values must match the C++ values in
  * ash::DisplayManager.
  * @enum {number}
@@ skipping 80 matching lines @@
      * @type {boolean}
      * @private
      */
     unifiedDesktopEnabled_: false,
 
     /**
      * Whether the unified desktop option should be present.
      * @type {boolean}
      * @private
      */
-    showUnifiedDesktopOption_: false,
+    unifiedEnabled_: false,
+
+    /**
+     * Whether the mirroring option should be present.
+     * @type {boolean}
+     * @private
+     */
+    mirroredEnabled_: false,
 
     /**
      * The array of current output displays.  It also contains the display
      * rectangles currently rendered on screen.
      * @type {!Array<!options.DisplayInfo>}
      * @private
      */
     displays_: [],
 
     /**
@@ skipping 114 matching lines @@
       for (var i = 0; i < optionTitles.length; i++)
         optionTitles[i].style.width = maxSize + 'px';
       chrome.send('getDisplayInfo');
     },
 
     /** @override */
     canShowPage: function() { return this.enabled_; },
 
     /**
      * Enables or disables the page. When disabled, the page will not be able to
-     * open, and will close if currently opened.
-     * @param {boolean} enabled Whether the page should be enabled.
-     * @param {boolean} showUnifiedDesktop Whether the unified desktop option
-     *     should be present.
+     * open, and will close if currently opened. Also sets the enabled states of
+     * mirrored and unifed desktop.
+     * @param {boolean} uiEnabled
+     * @param {boolean} unifiedEnabled
+     * @param {boolean} mirroredEnabled
      */
-    setEnabled: function(enabled, showUnifiedDesktop) {
-      this.showUnifiedDesktopOption_ = showUnifiedDesktop;
-      if (this.enabled_ == enabled)
+    setEnabled: function(uiEnabled, unifiedEnabled, mirroredEnabled) {
+      this.unifiedEnabled_ = unifiedEnabled;
+      this.mirroredEnabled_ = mirroredEnabled;
+      if (this.enabled_ == uiEnabled)
         return;
-      this.enabled_ = enabled;
-      if (!enabled && this.visible)
+      this.enabled_ = uiEnabled;
+      if (!uiEnabled && this.visible)
         PageManager.closeOverlay();
     },
 
     /**
      * Mouse move handler for dragging display rectangle.
      * @param {Event} e The mouse move event.
      * @private
      */
     onMouseMove_: function(e) {
       return this.processDragging_(e, {x: e.pageX, y: e.pageY});
@@ skipping 217 matching lines @@
       var arrow = $('display-configuration-arrow');
       arrow.hidden = false;
       // Adding 1 px to the position to fit the border line and the border in
       // arrow precisely.
       arrow.style.top = $('display-configurations').offsetTop -
           arrow.offsetHeight / 2 + 'px';
       arrow.style.left = displayLayout.div.offsetLeft +
           displayLayout.div.offsetWidth / 2 - arrow.offsetWidth / 2 + 'px';
 
       $('display-options-set-primary').disabled = display.isPrimary;
-      $('display-options-select-mirroring').disabled =
-          (this.displays_.length <= 1 && !this.unifiedDesktopEnabled_);
+      $('display-options-select-mirroring').disabled = !this.mirroredEnabled_;
       $('selected-display-start-calibrating-overscan').disabled =
           display.isInternal;
 
       var orientation = $('display-options-orientation-selection');
       orientation.disabled = this.unifiedDesktopEnabled_;
 
       var orientationOptions = orientation.getElementsByTagName('option');
       var orientationIndex = Math.floor(display.rotation / 90);
       orientationOptions[orientationIndex].selected = true;
 
@@ skipping 191 matching lines @@
 
       this.resetDisplaysView_();
       if (this.mirroring_)
         this.layoutMirroringDisplays_();
       else
         this.layoutDisplays_();
 
       $('display-options-select-mirroring').value =
           mirroring ? 'mirroring' : 'extended';
 
-      $('display-options-unified-desktop').hidden =
-          !this.showUnifiedDesktopOption_;
+      $('display-options-unified-desktop').hidden = !this.unifiedEnabled_;
 
       $('display-options-toggle-unified-desktop').checked =
           this.unifiedDesktopEnabled_;
 
       var disableUnifiedDesktopOption =
           (this.mirroring_ ||
            (!this.unifiedDesktopEnabled_ && this.displays_.length == 1));
 
       $('display-options-toggle-unified-desktop').disabled =
           disableUnifiedDesktopOption;
 
       this.updateSelectedDisplayDescription_();
     }
   };
 
   DisplayOptions.setDisplayInfo = function(mode, displays) {
     DisplayOptions.getInstance().onDisplayChanged_(mode, displays);
   };
 
   // Export
   return {
     DisplayOptions: DisplayOptions
   };
 });