Speed up object-keyed Map and Set by giving out sequential hash codes

src/collection.js

Index: src/collection.js
diff --git a/src/collection.js b/src/collection.js
index 6b468f5fc0ee8b2de8cd61ca1a27e4c78c8dcfb5..1cc6857b3c4330c2782b6856c8bb9e471e9be8f7 100644
--- a/src/collection.js
+++ b/src/collection.js
@@ -16,11 +16,6 @@ var $getExistingHash;
 var GlobalMap = global.Map;
 var GlobalObject = global.Object;
 var GlobalSet = global.Set;
-var IntRandom;
-
-utils.Import(function(from) {
-  IntRandom = from.IntRandom;
-});
 
 var NumberIsNaN;
 
@@ -110,11 +105,16 @@ function GetExistingHash(key) {
 %SetForceInlineFlag(GetExistingHash);
 
 
+var hashCounter = 1;
+
+
 function GetHash(key) {
   var hash = GetExistingHash(key);
   if (IS_UNDEFINED(hash)) {
-    hash = IntRandom() | 0;
-    if (hash === 0) hash = 1;
+    hash = hashCounter;
+    // Avoid a hash of zero, reserved for the hidden string. Also avoid
+    // non-Smi hashes.
+    hashCounter = hash == 0x3fffffff ? 1 : hash + 1;
     SET_PRIVATE(key, hashCodeSymbol, hash);
   }
   return hash;