Lock the prototype of internal classes.

src/uri.js

Index: src/uri.js
diff --git a/src/uri.js b/src/uri.js
index 72ca6f1565daa2d1b755e73622486afa4e1ddfc5..c910d756b4c4cdc96336ba49cf0ea25bc3611fb6 100644
--- a/src/uri.js
+++ b/src/uri.js
@@ -392,8 +392,9 @@ function URIUnescape(str) {
 
 // -------------------------------------------------------------------
 
-function SetupURI() {
-  // Setup non-enumerable URI functions on the global object and set
+function SetUpUri() {
+  %CheckIsBootstrapping();
+  // Set up non-enumerable URI functions on the global object and set
   // their names.
   InstallFunctions(global, DONT_ENUM, $Array(
     "escape", URIEscape,
@@ -405,4 +406,4 @@ function SetupURI() {
   ));
 }
 
-SetupURI();
+SetUpUri();