Split SkSL and utils apart again into .gni files.

Also extend GN format presubmit check to .gni files.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3976

Change-Id: I292f3136437101e3e2c3271e260536ab7a24b192
Reviewed-on: https://skia-review.googlesource.com/3976
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/gn/sksl.gni b/gn/sksl.gni
new file mode 100644
index 0000000..b76baec
--- /dev/null
+++ b/gn/sksl.gni
@@ -0,0 +1,19 @@
+# Copyright 2016 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Things are easiest for everyone if these source paths are absolute.
+_src = get_path_info("../src", "abspath")
+
+skia_sksl_sources = [
+  "$_src/sksl/SkSLCFGGenerator.cpp",
+  "$_src/sksl/SkSLCompiler.cpp",
+  "$_src/sksl/SkSLIRGenerator.cpp",
+  "$_src/sksl/SkSLParser.cpp",
+  "$_src/sksl/SkSLGLSLCodeGenerator.cpp",
+  "$_src/sksl/SkSLSPIRVCodeGenerator.cpp",
+  "$_src/sksl/SkSLUtil.cpp",
+  "$_src/sksl/ir/SkSLSymbolTable.cpp",
+  "$_src/sksl/ir/SkSLType.cpp",
+]