MD Settings: clarify "controlled by" logic

third_party/closure_compiler/interfaces/settings_private_interface.js

 // Copyright 2016 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.
 
 // This file was generated by:
 //   tools/json_schema_compiler/compiler.py.
 
 /** @fileoverview Interface for settingsPrivate that can be overriden. */
 
 assertNotReached('Interface file for Closure Compiler should not be executed.');
@@ skipping 22 matching lines @@
 
   /**
    * Gets the value of a specific pref.
    * @param {string} name
    * @param {function(!chrome.settingsPrivate.PrefObject):void} callback
    * @see https://developer.chrome.com/extensions/settingsPrivate#method-getPref
    */
   getPref: assertNotReached,
 
   /**
-   * Gets the page zoom factor.
+   * Gets the default page zoom factor. Possible values are currently between
+   * 0.25 and 5. For a full list, see zoom::kPresetZoomFactors.
    * @param {function(number):void} callback
    * @see https://developer.chrome.com/extensions/settingsPrivate#method-getDefaultZoom
    */
   getDefaultZoom: assertNotReached,
 
   /**
-   * Sets the page zoom factor.
+   * Sets the page zoom factor. Must be less than 0.001 different than a value
+   * in zoom::kPresetZoomFactors.
    * @param {number} zoom
    * @param {function(boolean):void=} callback
    * @see https://developer.chrome.com/extensions/settingsPrivate#method-setDefaultZoom
    */
   setDefaultZoom: assertNotReached,
 };
 
 /**
  * <p>Fired when a set of prefs has changed.</p><p>|prefs| The prefs that
  * changed.</p>
  * @type {!ChromeEvent}
  * @see https://developer.chrome.com/extensions/settingsPrivate#event-onPrefsChanged
  */
 SettingsPrivate.prototype.onPrefsChanged;