Copy junit-runner files into test-runner.

The android.test.runner target forms part of the Android API and
so must maintain backwards compatibility. The junit classes that
belong in there are copied here to ensure that they do not
change when external/junit is upgraded.

Bug: 30188076
Test: make checkbuild and checked android.test.runner contents
Change-Id: I947144c47ae1c3eb361a43c39bdd03dc11b9575f
diff --git a/test-runner/src/junit/runner/TestSuiteLoader.java b/test-runner/src/junit/runner/TestSuiteLoader.java
new file mode 100644
index 0000000..9cc6d81
--- /dev/null
+++ b/test-runner/src/junit/runner/TestSuiteLoader.java
@@ -0,0 +1,11 @@
+package junit.runner;
+
+/**
+ * An interface to define how a test suite should be loaded.
+ *
+ */
+//  TODO: deprecate
+public interface TestSuiteLoader {
+    abstract public Class load(String suiteClassName) throws ClassNotFoundException;
+    abstract public Class reload(Class aClass) throws ClassNotFoundException;
+}