Move kAuto and kFixed into a tighter scope than blink::

blink::kAuto and blink::kFixed from the enum LengthType is often
shadowed by other kAuto and other kFixed which triggers a ton of
warnings when trying to enable -Wshadow. This makes enum LengthType
into e class enum in Length, named Type. (So it will be be
Length::kAuto instead of just kAuto)

Bug: 925310
Change-Id: I6da0577c1a52954229297d9e0d81cb93fda60376
Reviewed-on: https://chromium-review.googlesource.com/c/1437282
Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632694}
13 files changed