Clean up Modifiers, DSLModifiers and ModifierFlags.

ModifierFlags have been moved out to a dedicated separate header.

Modifiers replaces the old DSLModifiers; it's a simple class
holding a position, a layout, and modifier flags. It's used by
the Parser and most Convert functions to pass modifiers around.

DSLModifiers is now redundant and has been removed.

Change-Id: Ib64893fad182b72656eed3da8cc78ce18e64856c
Bug: b/40045537
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/732857
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Arman Uguray <armansito@google.com>
Commit-Queue: Arman Uguray <armansito@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
53 files changed