Mojo: Move public/tests/test_{support,utils}.* to public/{c,cpp}/test_support.

mojo/public/c/DEPS

Index: mojo/public/c/DEPS
diff --git a/mojo/public/c/DEPS b/mojo/public/c/DEPS
index b7a363c7a6a8aa7930d17b650fb6e3735c50170d..52727706c3865337742c382cf59aa3bb0f394b5a 100644
--- a/mojo/public/c/DEPS
+++ b/mojo/public/c/DEPS
@@ -4,3 +4,13 @@ include_rules = [
   # But everyone can depend on the C system headers.
   "+mojo/public/c/system",
 ]
+
+specific_include_rules = {
+  r".*_(unit|perf)test\.cc": [
+    "+testing",
+    # Our test harness is C++, so allow the use of C++:
+    "+mojo/public/cpp/system",
+    "+mojo/public/cpp/test_support",
+    "+mojo/public/cpp/utility",
+  ],
+}