IndexedDB: Replace custom binding logic with [SetWrapperReferenceTo]

LayoutTests/storage/indexeddb/key-cursor-request-cycle-expected.txt

-Verify that that cursors weakly hold request, and work if request is GC'd
+Verify that that key cursors weakly hold request, and work if request is GC'd
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 
 indexedDB = self.indexedDB || self.webkitIndexedDB || self.mozIndexedDB || self.msIndexedDB || self.OIndexedDB;
 
-dbname = "cursor-request-cycle.html"
+dbname = "key-cursor-request-cycle.html"
 indexedDB.deleteDatabase(dbname)
 indexedDB.open(dbname)
 
 prepareDatabase():
 db = event.target.result
 store = db.createObjectStore('store')
 
 onOpen():
 db = event.target.result
 tx = db.transaction('store')
 store = tx.objectStore('store')
-cursorRequest = store.openCursor()
+cursorRequest = store.openKeyCursor()
 otherRequest = store.get(0)
 
 openCursorRequestSuccess():
 Result will be checked later, to ensure that lazy access is safe
 
 otherRequestSuccess():
 Verify that the request's result can be accessed lazily:
 gc()
 cursor = cursorRequest.result
 PASS cursor is non-null.
 PASS cursor.key is "key1"
-PASS cursor.value is "value1"
 cursorRequest.extra = 123
 cursor.extra = 456
 Ensure request is not released if cursor is still around.
 cursorRequest = null
 gc()
 PASS cursorRequestObservation.wasCollected is false
 cursor.continue()
 cursor = null
 gc()
 PASS cursorObservation.wasCollected is false
 finalRequest = store.get(0)
 
 cursorContinueSuccess():
 cursor = event.target.result
 PASS cursor is non-null.
 PASS cursor.key is "key2"
-PASS cursor.value is "value2"
 PASS event.target.extra is 123
 PASS cursor.extra is 456
 
 finalRequestSuccess():
 PASS cursor.key is "key2"
-PASS cursor.value is "value2"
 cursor = null
 gc()
 PASS cursorRequestObservation.wasCollected is true
 PASS cursorObservation.wasCollected is true
 PASS successfullyParsed is true
 
 TEST COMPLETE