Prevent extensions from clobbering JSON implementation that extension calls use

chrome/test/data/extensions/api_test/messaging/connect/test.html

Index: chrome/test/data/extensions/api_test/messaging/connect/test.html
diff --git a/chrome/test/data/extensions/api_test/messaging/connect/test.html b/chrome/test/data/extensions/api_test/messaging/connect/test.html
index 3e249165cd5dc28dc87d90caf103041581051885..4983a751daecd4dd587765cb03010b0091c46d7f 100644
--- a/chrome/test/data/extensions/api_test/messaging/connect/test.html
+++ b/chrome/test/data/extensions/api_test/messaging/connect/test.html
@@ -1,4 +1,20 @@
 <script>
+JSON.parse = function() {
+  return "JSON.parse clobbered by extension.";
+}
+
+JSON.stringify = function() {
+  return "JSON.stringify clobbered by extension.";
+}
+
+Array.prototype.toJSON = function() {
+  return "Array.prototype.toJSON clobbered by extension.";
+}
+
+Object.prototype.toJSON = function() {
+  return "Object.prototype.toJSON clobbered by extension.";
+}
+
 // Keep track of the tab that we're running tests in, for simplicity.
 var testTab = null;