Throw an exception if media playbackRate is out of range.

Intent to implement/ship: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/a0tguvcZZyk

BUG: 747082
Change-Id: I740aa8396a7cecc74b741ab544c71652121c44d3
Reviewed-on: https://chromium-review.googlesource.com/666121
Commit-Queue: apacible <apacible@chromium.org>
Reviewed-by: Dimitri Glazkov <dglazkov@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509282}
8 files changed