added SkSL to Skia build

skia/BUILD.gn

Index: skia/BUILD.gn
diff --git a/skia/BUILD.gn b/skia/BUILD.gn
index 43342b61a15a7f8038c627262405a4843b1762e0..178b6945b49a8e9e3272adbf18285fa0b74a70e3 100644
--- a/skia/BUILD.gn
+++ b/skia/BUILD.gn
@@ -80,6 +80,7 @@ config("skia_library_config") {
     "//third_party/skia/src/pdf",
     "//third_party/skia/src/ports",
     "//third_party/skia/src/sfnt",
+    "//third_party/skia/src/sksl",
     "//third_party/skia/src/utils",
     "//third_party/skia/src/lazy",
   ]
@@ -173,6 +174,7 @@ component("skia") {
   # The skia gypi values are relative to the skia_dir, so we need to rebase.
   sources += skia_core_sources
   sources += skia_effects_sources
+  sources += skia_sksl_sources
   sources += skia_utils_sources
   sources += [
     "//third_party/skia/src/fonts/SkFontMgr_indirect.cpp",