GuestView constants are now frozen (and thus actually constant).

BUG=466136

Review URL: https://codereview.chromium.org/1028503003

Cr-Commit-Position: refs/heads/master@{#321594}

extensions/renderer/resources/guest_view/extension_view/extension_view_constants.js

@@ -6,9 +6,9 @@
 
 // Container for the extensionview constants.
 var ExtensionViewConstants = {
-
+  // Attributes.
   ATTRIBUTE_EXTENSION: 'extension',
   ATTRIBUTE_SRC: 'src',
 };
 
-exports.ExtensionViewConstants = ExtensionViewConstants;
\ No newline at end of file
+exports.ExtensionViewConstants = $Object.freeze(ExtensionViewConstants);

extensions/renderer/resources/guest_view/web_view/web_view_constants.js

@@ -40,4 +40,4 @@ var WebViewConstants = {
       'The permission request for "%1" has been denied.'
 };
 
-exports.WebViewConstants = WebViewConstants;
+exports.WebViewConstants = $Object.freeze(WebViewConstants);

extensions/renderer/safe_builtins.cc

@@ -66,8 +66,8 @@ const char kScript[] =
     "// Save only what is needed by the extension modules.\n"
     "saveBuiltin(Object,\n"
     "            ['hasOwnProperty'],\n"
-    "            ['create', 'defineProperty', 'getOwnPropertyDescriptor',\n"
-    "             'getPrototypeOf', 'keys']);\n"
+    "            ['create', 'defineProperty', 'freeze',\n"
+    "             'getOwnPropertyDescriptor', 'getPrototypeOf', 'keys']);\n"
     "saveBuiltin(Function,\n"
     "            ['apply', 'bind', 'call']);\n"
     "saveBuiltin(Array,\n"