Program is now immutable*, and remains part of the public Tint
interface.
ProgramBuilder is the mutable builder for Programs, and is not part of
the public Tint interface. ast::Builder has been folded into
ProgramBuilder.
Immutable Programs can be cloned into a mutable ProgramBuilder with
Program::CloneAsBuilder().
Mutable ProgramBuilders can be moved into immutable Programs.
* - mostly immutable. It still has a move constructor and move
assignment operator - required for practical usage - and the
semantic information on AST nodes is still mutable.
Bug: tint:390
Change-Id: Ia856c50b1880c2f95c91467a9eef5024cbc380c6
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/38240
Reviewed-by: dan sinclair <dsinclair@chromium.org>
a6b9a8eb2f