Modern IDB: IDBObjectStore.add() support.

Modern IDB: IDBObjectStore.add() support.
https://bugs.webkit.org/show_bug.cgi?id=150711

Reviewed by Alex Christensen.

Source/WebCore:

Test: storage/indexeddb/modern/basic-add.html

* Modules/indexeddb/client/IDBObjectStoreImpl.cpp:
(WebCore::IDBClient::IDBObjectStore::add):

* Modules/indexeddb/client/IDBTransactionImpl.cpp:
(WebCore::IDBClient::IDBTransaction::requestGetRecord):

LayoutTests:

* storage/indexeddb/modern/basic-add-expected.txt: Added.
* storage/indexeddb/modern/basic-add.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@191795 268f45cc-cd09-0410-ab3c-d52691b4dbfc