Add setting to isolate zoom changes by default.

chrome/browser/resources/options/browser_options.js

Index: chrome/browser/resources/options/browser_options.js
diff --git a/chrome/browser/resources/options/browser_options.js b/chrome/browser/resources/options/browser_options.js
index 96283c3d8b4cd069c9555a1113b6eace1f524bb4..c256d7178ed2945f5de7c0b20f4a5979fbf74137 100644
--- a/chrome/browser/resources/options/browser_options.js
+++ b/chrome/browser/resources/options/browser_options.js
@@ -682,6 +682,10 @@ cr.define('options', function() {
         chrome.send('defaultZoomFactorAction',
             [String(event.target.options[event.target.selectedIndex].value)]);
       };
+      $('defaultZoomScope').onchange = function(event) {
+        chrome.send('defaultZoomScopeAction',
+            [event.target.checked]);
+      };
       $('safeBrowsingExtendedReportingCheckbox').onchange = function(event) {
         chrome.send('safeBrowsingExtendedReportingAction',
             [event.target.checked]);
@@ -2020,6 +2024,15 @@ cr.define('options', function() {
     },
 
     /**
+     * Set the checked state of the default zoom scope checkbox.
+     * @param {boolean} checked Whether to check the checkbox.
+     * @private
+     */
+    setupZoomScopeCheckbox_: function(checked) {
+      $('defaultZoomScope').checked = checked;
+    },
+
+    /**
      * Shows/hides the autoOpenFileTypesResetToDefault button and label, with
      * animation.
      * @param {boolean} display Whether to show the button and label or not.
@@ -2419,6 +2432,7 @@ cr.define('options', function() {
     'setWallpaperManaged',
     'setupPageZoomSelector',
     'setupProxySettingsButton',
+    'setupZoomScopeCheckbox',
     'showCreateProfileError',
     'showCreateProfileSuccess',
     'showCreateProfileWarning',