Add RuntimeBlendUtils to bazel.

This should allow http://review.skia.org/428617 to reland.

Change-Id: I85a79951c687323b97784d3a606dba2eaa3fd420
Bug: skia:12080
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/428619
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
diff --git a/public.bzl b/public.bzl
index c8f64b1..d45d1a4 100644
--- a/public.bzl
+++ b/public.bzl
@@ -606,6 +606,8 @@
         "tools/ResourceFactory.h",
         "tools/Resources.cpp",
         "tools/Resources.h",
+        "tools/RuntimeBlendUtils.cpp",
+        "tools/RuntimeBlendUtils.h",
         "tools/SkMetaData.cpp",
         "tools/SkMetaData.h",
         "tools/SkSharingProc.cpp",