bazel: refactor SkSL private headers into own filegroup.

Files in :private_hdrs map to gn/core.gni and :sksl_private_hdrs
maps to gn/sksl.gni.

Bug: skia:13485
Change-Id: I9f97d88b886ac53faffbf9ca51d743b543785aa1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/568039
Reviewed-by: Kevin Lubick <kjlubick@google.com>
diff --git a/include/private/BUILD.bazel b/include/private/BUILD.bazel
index 956a272..1c301bf 100644
--- a/include/private/BUILD.bazel
+++ b/include/private/BUILD.bazel
@@ -7,6 +7,23 @@
     visibility = ["//tools/skui:__pkg__"],
 )
 
+# In own filegroup for mapping to the //gn/sksl.gni file.
+filegroup(
+    name = "sksl_private_hdrs",
+    srcs = [
+        "SkSLDefines.h",
+        "SkSLIRNode.h",
+        "SkSLLayout.h",
+        "SkSLModifiers.h",
+        "SkSLProgramElement.h",
+        "SkSLProgramKind.h",
+        "SkSLSampleUsage.h",
+        "SkSLStatement.h",
+        "SkSLString.h",
+        "SkSLSymbol.h",
+    ],
+)
+
 filegroup(
     name = "private_hdrs",
     srcs = [
@@ -29,16 +46,6 @@
         "SkOnce.h",
         "SkOpts_spi.h",
         "SkPathRef.h",
-        "SkSLDefines.h",
-        "SkSLIRNode.h",
-        "SkSLLayout.h",
-        "SkSLModifiers.h",
-        "SkSLProgramElement.h",
-        "SkSLProgramKind.h",
-        "SkSLSampleUsage.h",
-        "SkSLStatement.h",
-        "SkSLString.h",
-        "SkSLSymbol.h",
         "SkSafe32.h",
         "SkSafe_math.h",
         "SkSemaphore.h",
@@ -58,6 +65,7 @@
         "SkUniquePaintParamsID.h",
         "SkVx.h",
         "SkWeakRefCnt.h",
+        ":sksl_private_hdrs",
         "//include/private/chromium:private_hdrs",
     ] + select({
         "//src/gpu:has_gpu_backend": [