Fixed an issue with sksl variable declarations

There was an issue where multiple variables defined in the same
declaration were not being sequenced appropriately during analysis, so
'int x = 0, y = x + 1' would report that x was undefined.

Bug: skia:
Change-Id: I882f7e216467306f6a6013a0a34aac30a4c60744
Reviewed-on: https://skia-review.googlesource.com/18313
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
9 files changed