IndexedDB: Make WebIDBCallbacks API match IndexedDBCallbacksImpl

This is the first step to merging WebIDBCallbacksImpl and
IndexedDBCallbacksImpl.  In this step, WebIDBCallbacks APIs are
updated to match IndexedDBCallbacksImpl, which implements the mojom
IDBCallbacks interface.

As part of this step, all of the functionality of
IndexedDBCallbacksImpl for each call is moved to the associated
WebIDBCallbacks implementation.  In some cases, that is
WebIDBCallbacksImpl.  In others, it's an implementation in a
different class.

Once the APIs match, a later CL will delete IndexedDBCallbacksImpl,
update the class hierarchy for WebIDBCallbacks to be based on the
mojom type, and update references to the old IndexedDBCallbacksImpl
callbacks class to WebIDBCallbacksImpl instances.

Bug: 717812
Change-Id: I405b603aaac72ceafa7c4189afb55040e1b3b502
Reviewed-on: https://chromium-review.googlesource.com/c/1371207
Commit-Queue: Chase Phillips <cmp@chromium.org>
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621829}
15 files changed