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

chrome/test/data/extensions/platform_apps/restrictions/main.js

Index: chrome/test/data/extensions/platform_apps/restrictions/main.js
diff --git a/chrome/test/data/extensions/platform_apps/restrictions/main.js b/chrome/test/data/extensions/platform_apps/restrictions/main.js
index 39fa4b72a32a33a48e70de0e1b1c40a58f502c87..39a309f638eed192c285966259f3c514580ee748 100644
--- a/chrome/test/data/extensions/platform_apps/restrictions/main.js
+++ b/chrome/test/data/extensions/platform_apps/restrictions/main.js
@@ -62,10 +62,11 @@ chrome.test.runTests([
   },
 
   function testHistory() {
-    // Accessing these logs warnings to the console.
-    assertEq('undefined', typeof(history.back));
-    assertEq('undefined', typeof(history.forward));
-    assertEq('undefined', typeof(history.length));
+    // History API should be disabled (e.g. Accessing these logs warnings to
+    // the console).
+    for (var property in history) {
+      assertEq('undefined', typeof(history[property]));

[Inactive, 2014/04/21 19:46:10]

This is a bit safer now, in case new properties / methods are added to History
but we don't explicitly disable them in platform_app.js (as we now have to
disable / remove API explicitly).

Also, this adds coverage for history.go(), which was not tested before but
should be disabled.

+    }
 
     // These are part of the HTML5 History API that are feature detected, so we
     // remove them altogether, allowing apps to have fallback behavior.