Eliminate DSLBlock class.

Blocks are now represented by DSLStatements. DSLBlocks were helpful
for hand-written DSL, but while parsing, they don't really add value.
This saves a small amount of code size (~0.6K).

Change-Id: Ia81f4454190f636f5832ccd207f2c0ea5fb3b6fc
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/694618
Reviewed-by: James Godfrey-Kittle <jamesgk@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
13 files changed