IndexedDB: map key range mojom to blink IDBKeyRange

Bug: 717812
Change-Id: I0cacbf8a384af330978ccc4ea72e755427b84d1b
Reviewed-on: https://chromium-review.googlesource.com/c/1357535
Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Chase Phillips <cmp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614890}
22 files changed