Optimize isFinite and isNaN.

src/array.js

Index: src/array.js
diff --git a/src/array.js b/src/array.js
index 32a370fda862f81c293b3b39f6a075438ae96ec5..281c507f5a6d6e83b4dd196e3170a0538950fa33 100644
--- a/src/array.js
+++ b/src/array.js
@@ -1314,13 +1314,12 @@ function ArrayIsArray(obj) {
 
 
 // -------------------------------------------------------------------
-function SetUpArray() {
-  %CheckIsBootstrapping();
-  // Set up non-enumerable constructor property on the Array.prototype
+function SetupArray() {
+  // Setup non-enumerable constructor property on the Array.prototype
   // object.
   %SetProperty($Array.prototype, "constructor", $Array, DONT_ENUM);
 
-  // Set up non-enumerable functions on the Array object.
+  // Setup non-enumerable functions on the Array object.
   InstallFunctions($Array, DONT_ENUM, $Array(
     "isArray", ArrayIsArray
   ));
@@ -1338,7 +1337,7 @@ function SetUpArray() {
     return f;
   }
 
-  // Set up non-enumerable functions of the Array.prototype object and
+  // Setup non-enumerable functions of the Array.prototype object and
   // set their names.
   // Manipulate the length of some of the functions to meet
   // expectations set by ECMA-262 or Mozilla.
@@ -1369,13 +1368,19 @@ function SetUpArray() {
   %FinishArrayPrototypeSetup($Array.prototype);
 
   // The internal Array prototype doesn't need to be fancy, since it's never
-  // exposed to user code.
-  // Adding only the functions that are actually used.
-  SetUpLockedPrototype(InternalArray, $Array(), $Array(
-    "join", getFunction("join", ArrayJoin),
-    "pop", getFunction("pop", ArrayPop),
-    "push", getFunction("push", ArrayPush)
-  ));
+  // exposed to user code, so no hidden prototypes or DONT_ENUM attributes
+  // are necessary.
+  // The null __proto__ ensures that we never inherit any user created
+  // getters or setters from, e.g., Object.prototype.
+  InternalArray.prototype.__proto__ = null;
+  // Adding only the functions that are actually used, and a toString.
+  InternalArray.prototype.join = getFunction("join", ArrayJoin);
+  InternalArray.prototype.pop = getFunction("pop", ArrayPop);
+  InternalArray.prototype.push = getFunction("push", ArrayPush);
+  InternalArray.prototype.toString = function() {
+    return "Internal Array, length " + this.length;
+  };
 }
 
-SetUpArray();
+
+SetupArray();