Update platform_app.js to work even if window.history is not replaceable

chrome/renderer/resources/extensions/platform_app.js

Index: chrome/renderer/resources/extensions/platform_app.js
diff --git a/chrome/renderer/resources/extensions/platform_app.js b/chrome/renderer/resources/extensions/platform_app.js
index 0982a6a18ea0b4371208292f1fd14f6ed4d3b921..829fa3fe4c2d484bdc78f9b629781dec75da21a4 100644
--- a/chrome/renderer/resources/extensions/platform_app.js
+++ b/chrome/renderer/resources/extensions/platform_app.js
@@ -75,6 +75,22 @@ function disableMethods(object, objectName, methodNames, useThrowingStubs) {
 }
 
 /**
+ * Deletes the given methods from the passed in objext.
+ *
+ * This may be needed for feature detection as ('methodName' in object) will
+ * return false after this.
+ *
+ * @param {Object} object The object with methods to disable. The prototype is
+ *     preferred.
+ * @param {Array.<string>} methodNames names of methods to delete.
+ */
+function deleteMethods(object, methodNames) {
+  $Array.forEach(methodNames, function(methodName) {
+    delete object[methodName];
+  });
+}
+
+/**
  * Replaces the given properties of the passed in object with stubs that log
  * 'not available' warnings to the console and return undefined when gotten. If
  * a property's setter is later invoked, the getter and setter are restored to
@@ -145,15 +161,33 @@ function disableSetters(object, objectName, propertyNames, opt_messageSuffix) {
   });
 }
 
+/**
+ * Deletes the given properties of the passed in object.
+ *
+ * This may be needed for feature detection as ('propertyName' in object) will
+ * return false after this.
+ *
+ * @param {Object} object The object with properties to disable.
+ * @param {Array.<string>} propertyNames names of properties to delete.
+ */
+function deleteProperties(object, propertyNames) {
+  $Array.forEach(propertyNames, function(propertyName) {
+    delete object[propertyName];
+  });
+}
+
 // Disable benign Document methods.
 disableMethods(HTMLDocument.prototype, 'document', ['open', 'clear', 'close']);
 
 // Replace evil Document methods with exception-throwing stubs.
 disableMethods(HTMLDocument.prototype, 'document', ['write', 'writeln'], true);
 
-// Disable history.
-window.history = {};

[arv (Not doing code reviews), 2014/04/22 13:54:42]

This one could have been replaced with a defineProperty instead.

[Inactive, 2014/04/22 14:43:54]

Would be much simpler, let me give this a try.

[Inactive, 2014/04/22 14:59:59]

Done, thanks. Much simpler indeed.

+// Disable history API.
 disableGetters(window.history, 'history', ['back', 'forward', 'go', 'length']);
+// These are part of the HTML5 History API that are feature detected, so we
+// remove them altogether, allowing apps to have fallback behavior.
+deleteProperties(window.history, ['state']);
+deleteMethods(History.prototype, ['pushState', 'replaceState']);
 
 // Disable find.
 disableMethods(Window.prototype, 'window', ['find']);