Add setting to isolate zoom changes by default.

chrome/browser/ui/webui/options/options_browsertest.js

Index: chrome/browser/ui/webui/options/options_browsertest.js
diff --git a/chrome/browser/ui/webui/options/options_browsertest.js b/chrome/browser/ui/webui/options/options_browsertest.js
index bbb019fea0d1f2675009f26c54794cacd111358d..3cb7f54e01843668182c813c4df273bc527f4f70 100644
--- a/chrome/browser/ui/webui/options/options_browsertest.js
+++ b/chrome/browser/ui/webui/options/options_browsertest.js
@@ -62,6 +62,7 @@ OptionsWebUITest.prototype = {
   preLoad: function() {
     this.makeAndRegisterMockHandler(
         ['defaultZoomFactorAction',
+         'defaultZoomScopeAction',
          'fetchPrefs',
          'observePrefs',
          'setBooleanPref',
@@ -203,6 +204,20 @@ TEST_F('OptionsWebUITest', 'testDefaultZoomFactor', function() {
 });
 
 /**
+ * Test the default zoom scope checkbox.
+ */
+TEST_F('OptionsWebUITest', 'testDefaultZoomScope', function() {
+  // Verify that the zoom scope checkbox exists.
+  var defaultZoomScope = $('defaultZoomScope');
+  assertNotEquals(defaultZoomScope, null);
+  var initialValue = $('defaultZoomScope').checked;
+
+  this.mockHandler.expects(once()).defaultZoomScopeAction([!initialValue]);
+  defaultZoomScope.click();
+  testDone();
+});
+
+/**
  * If |confirmInterstitial| is true, the OK button of the Do Not Track
  * interstitial is pressed, otherwise the abort button is pressed.
  * @param {boolean} confirmInterstitial Whether to confirm the Do Not Track