Implement AP2 Promises

LayoutTests/fast/js/Promise-then-in-workers-expected.txt

 [Worker] Test Promise.
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 Starting worker: resources/Promise-then-in-workers.js
-PASS [Worker] thisInInit === firstPromise is true
+PASS [Worker] thisInInit === firstPromise is false
+PASS [Worker] thisInInit === global is true
 PASS [Worker] firstPromise instanceof Promise is true
 PASS [Worker] secondPromise instanceof Promise is true
-PASS [Worker] firstPromise.then(null) threw exception TypeError: fulfillCallback must be a function or undefined.
-PASS [Worker] firstPromise.then(undefined, null) threw exception TypeError: rejectCallback must be a function or undefined.
-PASS [Worker] firstPromise.then(37) threw exception TypeError: fulfillCallback must be a function or undefined.
+PASS [Worker] firstPromise.then(null) threw exception TypeError: onFulfilled must be a function or undefined.
+PASS [Worker] firstPromise.then(undefined, null) threw exception TypeError: onRejected must be a function or undefined.
+PASS [Worker] firstPromise.then(37) threw exception TypeError: onFulfilled must be a function or undefined.
 PASS [Worker] thisInFulfillCallback === firstPromise is false
-PASS [Worker] thisInFulfillCallback === secondPromise is true
+PASS [Worker] thisInFulfillCallback === secondPromise is false
+PASS [Worker] thisInFulfillCallback === global is true
 PASS [Worker] result is "hello"
 PASS successfullyParsed is true
 
 TEST COMPLETE