Introduce font variation settings parser

Font variation settings enables developer to specify font axes for
configuring glyph looking. This CL parse Font Variation settings to
make a array of Axis. More work is needed for using parsed axes.

Bug: 33062398
Test: Done by unittests.
Change-Id: I529b98b28df1c738237bee0729d9f479bd656dd3
2 files changed