Add setting to isolate zoom changes by default.

chrome/browser/resources/options/browser_options.html

 <if expr="chromeos">
 <link rel="import" href="/people_page/lock_screen_constants.html">
 </if>
 <div id="settings" class="page" hidden>
   <header>
     <h1 i18n-content="settingsTitle"></h1>
   </header>
   <include src="automatic_settings_reset_banner.html">
 <if expr="chromeos">
   <link rel="import" href="chrome://resources/cr_elements/network/cr_network_icon.html">
@@ skipping 627 matching lines @@
             class="controlled-setting-indicator"></span>
         <button id="fontSettingsCustomizeFontsButton"
             i18n-content="fontSettingsCustomizeFontsButton"></button>
       </div>
       <div class="settings-row" guest-visibility="disabled">
         <label class="web-content-select-label">
           <span i18n-content="defaultZoomFactorLabel"></span>
           <select id="defaultZoomFactor" dataType="double"></select>
         </label>
       </div>
+      <div class="checkbox" guest-visibility="disabled">
+        <label>
+          <input id="defaultZoomScope" type="checkbox">
+          <span i18n-content="defaultZoomScopeLabel"></span>
+        </label>
+      </div>
 <if expr="is_macosx">
       <div class="checkbox">
         <label>
           <input id="tabsToLinksPref" pref="webkit.webprefs.tabs_to_links"
               metric="Options_TabsToLinks" type="checkbox">
           <span i18n-content="tabsToLinksPref"></span>
         </label>
       </div>
 </if>
     </div>
@@ skipping 477 matching lines @@
       </button>
     </div>
   </section>
   </div>  <!-- advanced-settings-container -->
   </div>  <!-- advanced-settings -->
   <footer id="advanced-settings-footer">
     <a is="action-link" id="advanced-settings-expander"
         i18n-content="showAdvancedSettings"></a>
   </footer>
 </div>