Move scoped_test_dir.* and test_io_thread.* from edk/test to edk/system/test.

mojo/edk/system/test/BUILD.gn

Index: mojo/edk/system/test/BUILD.gn
diff --git a/mojo/edk/system/test/BUILD.gn b/mojo/edk/system/test/BUILD.gn
index a31c3da5649c0297c629ad51bd4e3eb2382512a9..e91db656a8c9fab3a12e80a3bd5b1b4745c79b2e 100644
--- a/mojo/edk/system/test/BUILD.gn
+++ b/mojo/edk/system/test/BUILD.gn
@@ -10,12 +10,16 @@ mojo_edk_source_set("test") {
   sources = [
     "random.cc",
     "random.h",
+    "scoped_test_dir.cc",
+    "scoped_test_dir.h",
     "simple_test_thread.cc",
     "simple_test_thread.h",
     "sleep.cc",
     "sleep.h",
     "stopwatch.cc",
     "stopwatch.h",
+    "test_io_thread.cc",
+    "test_io_thread.h",
     "timeouts.cc",
     "timeouts.h",
   ]
@@ -30,7 +34,10 @@ mojo_edk_source_set("test") {
     "//base/test:test_support",
   ]
 
-  mojo_edk_deps = [ "mojo/edk/embedder:platform" ]
+  mojo_edk_deps = [
+    "mojo/edk/embedder:platform",
+    "mojo/edk/util",
+  ]
 }
 
 mojo_edk_source_set("unittests") {