Removing ASH friend in dom_keycode_converter build target

A component in ASH was directly including one of the now-private
inc files.  We want to keep that data private so this CL introduces
a header which exposes a DomCode[] to allow iterating over them w/o
directly including the data files.

CL which introduced this dependency:
https://chromium-review.googlesource.com/c/chromium/src/+/1058080

Change-Id: I78b1fe1447e1f6354e690e5ec6fdd7132f61c74d
Reviewed-on: https://chromium-review.googlesource.com/1091147
Reviewed-by: Gary Kacmarcik <[email protected]>
Reviewed-by: Tao Wu <[email protected]>
Commit-Queue: Joe Downing <[email protected]>
Cr-Commit-Position: refs/heads/master@{#568747}
3 files changed