move Sk{Test,Random}ScalerContext to tools

There's no need for Skia users to link this test code.

Change-Id: I9d6ef2a053d0cf5cb916aa254389ca819c48bae1
Reviewed-on: https://skia-review.googlesource.com/69922
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/public.bzl b/public.bzl
index 95f94c3..2d23bd7 100644
--- a/public.bzl
+++ b/public.bzl
@@ -438,6 +438,10 @@
         "tools/Resources.cpp",
         "tools/Resources.h",
         "tools/SkJSONCPP.h",
+        "tools/SkRandomScalerContext.cpp",
+        "tools/SkRandomScalerContext.h",
+        "tools/SkTestScalerContext.cpp",
+        "tools/SkTestScalerContext.h",
         "tools/UrlDataManager.cpp",
         "tools/UrlDataManager.h",
         "tools/debugger/*.cpp",