This reverts commit 193c16380f.
Reason for revert: fixed google3 warning
Original change's description:
> Revert "Eliminate DSLPossibleExpression."
>
> This reverts commit f2d000328f.
>
> Reason for revert: breaking google3 roll
>
> Original change's description:
> > Eliminate DSLPossibleExpression.
> >
> > The Possible(Expression|Statement) classes were added at
> > http://review.skia.org/375069. These classes were responsible for
> > capturing `__builtin_FILE()` and `__builtin_LINE()` when an
> > expression or statement was added to a hand-authored DSL program. This
> > allowed errors to be reported on the C++ file/line where they were
> > encountered. This was a good feature to have, when the plan was to
> > author the majority of SkSL code via DSL.
> >
> > Later, IRNode positions were converted from an integer line number to
> > SkSL Positions at http://review.skia.org/518137. This gave us range
> > tracking, but at a high memory cost (16 bytes per IRNode, versus four
> > bytes when we tracked line numbers only).
> >
> > Positions were reduced to 8 bytes at http://review.skia.org/521005 by
> > removing the filename, which was only used for hand-authored DSL. (The
> > size was pared all the way back to 4 bytes at
> > http://review.skia.org/533699 by packing the data more efficiently.)
> >
> > __builtin_FILE/LINE capturing was removed entirely at
> > http://review.skia.org/528366; the filename was discarded anyway and
> > the line number didn't have a range and wasn't very meaningful without
> > a filename. Also, it didn't matter very much since we no longer intended
> > to hand-craft our programs in DSL.
> >
> > At this stage, DSLPossibleExpression stopped adding value and simply
> > served to move Expressions around.
> >
> > Change-Id: I29ac33e08dcc1804cc0619c1e8856ba28ebcc51d
> > Reviewed-on: https://skia-review.googlesource.com/c/skia/+/542145
> > Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
> > Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
> > Auto-Submit: John Stiles <johnstiles@google.com>
>
> Change-Id: I33badbdcce8760200246bf50e4932d42721ea952
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/543078
> Reviewed-by: Tyler Denniston <tdenniston@google.com>
> Owners-Override: Kevin Lubick <kjlubick@google.com>
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Commit-Queue: Tyler Denniston <tdenniston@google.com>
Change-Id: I71f248b2343806f85cad5f0661470c95334bbe22
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/545236
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
c6218799a6