Lock the prototype of internal classes.

src/math.js

Index: src/math.js
diff --git a/src/math.js b/src/math.js
index 31306e79d18e1e98cba7e2ee7f697ef303f91543..b5a6d1811757aaaa7b0f35fc863b4a471e47b341 100644
--- a/src/math.js
+++ b/src/math.js
@@ -195,8 +195,9 @@ function MathTan(x) {
 
 // -------------------------------------------------------------------
 
-function SetupMath() {
-  // Setup math constants.
+function SetUpMath() {
+  %CheckIsBootstrapping();
+  // Set up math constants.
   // ECMA-262, section 15.8.1.1.
   %OptimizeObjectForAddingMultipleProperties($Math, 8);
   %SetProperty($Math,
@@ -236,7 +237,7 @@ function SetupMath() {
                DONT_ENUM |  DONT_DELETE | READ_ONLY);
   %ToFastProperties($Math);
 
-  // Setup non-enumerable functions of the Math object and
+  // Set up non-enumerable functions of the Math object and
   // set their names.
   InstallFunctionsOnHiddenPrototype($Math, DONT_ENUM, $Array(
     "random", MathRandom,
@@ -258,7 +259,6 @@ function SetupMath() {
     "max", MathMax,
     "min", MathMin
   ));
-};
-
+}
 
-SetupMath();
+SetUpMath();