Use Length::Is* functions instead of Length::GetType()

It makes the code more readable and reduces the amount of code
exposed to enum LengthType which will simplify future changes
of it.

Bug: 925310
Change-Id: Ie8e710086abdda2058535ea4ccf7d77871725fec
Reviewed-on: https://chromium-review.googlesource.com/c/1437633
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#626517}
11 files changed