The assertion was too strict, not matching the check in JSTypedArray::Create.
Delete the TODO because the code does not actually rely on the assertion for safety: EmitElementStore always performs a length check.
Drive-by-fix: KeyedAccessStoreMode::STANDARD_STORE is equally safe and does one comparison less.

Bug: chromium:724889
Change-Id: I988a4eb6ad36d35143a008f7289b075f5c05e7ed
Reviewed-on: https://chromium-review.googlesource.com/517102Reviewed-by: Daniel Clifford <danno@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45617}