Re-re-land sksl fragment processor support

This reverts commit 5ce397205528f82084fc650c2ce27d246c01da33.

Bug: skia:
Change-Id: I88260c90004610a1cf8ad1a87c2b4b222525bbb6
Reviewed-on: https://skia-review.googlesource.com/21108
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/gn/sksl.gni b/gn/sksl.gni
index a1cab82..8c74b30 100644
--- a/gn/sksl.gni
+++ b/gn/sksl.gni
@@ -11,11 +11,16 @@
   "$_src/sksl/SkSLCompiler.cpp",
   "$_src/sksl/SkSLIRGenerator.cpp",
   "$_src/sksl/SkSLParser.cpp",
+  "$_src/sksl/SkSLCPPCodeGenerator.cpp",
+  "$_src/sksl/SkSLHCodeGenerator.cpp",
   "$_src/sksl/SkSLGLSLCodeGenerator.cpp",
   "$_src/sksl/SkSLSPIRVCodeGenerator.cpp",
   "$_src/sksl/SkSLString.cpp",
   "$_src/sksl/SkSLUtil.cpp",
   "$_src/sksl/lex.layout.cpp",
   "$_src/sksl/ir/SkSLSymbolTable.cpp",
+  "$_src/sksl/ir/SkSLSetting.cpp",
   "$_src/sksl/ir/SkSLType.cpp",
 ]
+
+skia_gpu_processor_sources = [ "$_src/gpu/effects/GrDitherEffect.fp" ]