Add {Map,Set}::FromArray to the API

src/collection.js

Index: src/collection.js
diff --git a/src/collection.js b/src/collection.js
index 6b468f5fc0ee8b2de8cd61ca1a27e4c78c8dcfb5..1c6b475df6cf4761f4d25738150b1d3bfa3c44d5 100644
--- a/src/collection.js
+++ b/src/collection.js
@@ -4,6 +4,8 @@
 
 var $getHash;
 var $getExistingHash;
+var $mapFromArray;
+var $setFromArray;
 
 (function(global, utils) {
 "use strict";
@@ -480,4 +482,23 @@ utils.InstallFunctions(GlobalMap.prototype, DONT_ENUM, [
 $getHash = GetHash;
 $getExistingHash = GetExistingHash;
 
+$mapFromArray = function(array) {
+  var map = new GlobalMap;
+  var length = array.length;
+  for (var i = 0; i < length; ++i) {
+    var entry = array[i];
+    %_CallFunction(map, entry[0], entry[1], MapSet);
+  }
+  return map;
+};
+
+$setFromArray = function(array) {
+  var set = new GlobalSet;
+  var length = array.length;
+  for (var i = 0; i < length; ++i) {
+    %_CallFunction(set, array[i], SetAdd);
+  }
+  return set;
+};
+
 })