IndexedDB: Update IDBObserverChanges to stop using WebIDBObservation

Bug: 717812
Change-Id: I2bd4419ce86555ed0041d07a23adc31cdc0d4253
Reviewed-on: https://chromium-review.googlesource.com/c/1366478
Commit-Queue: Chase Phillips <cmp@chromium.org>
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616809}
5 files changed