Revert "removed SkSLLayoutLexer"

This reverts commit 804f81786148cd3a4385d10ab7a31340fa47b10d.

Reason for revert: breaking chrome roll: https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8940111858576531488/+/steps/compile__with_patch_/0/stdout

Original change's description:
> removed SkSLLayoutLexer
> 
> Bug: skia:
> Change-Id: Iad4c89fbde8bc1f6c3d022af9aec2ec5faa8a4ef
> Reviewed-on: https://skia-review.googlesource.com/142583
> Reviewed-by: Mike Klein <mtklein@google.com>
> Commit-Queue: Ethan Nicholas <ethannicholas@google.com>

TBR=mtklein@google.com,ethannicholas@google.com

Change-Id: Ie07065ac43c5b8356665a7170adbe97ae8fd9f90
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/143120
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
6 files changed