Add infrastructure for registering built-in native methods.

While I'm here, make fiddling with Thread state easier.

Change-Id: I3d215a3a852aa8970c3974b2edefce9dd261ccd7
diff --git a/src/jni_internal_test.cc b/src/jni_internal_test.cc
index 42ab158..3e3e381 100644
--- a/src/jni_internal_test.cc
+++ b/src/jni_internal_test.cc
@@ -283,7 +283,7 @@
 
   // Check that registering native methods is successful
   {
-    JNINativeMethod methods[] = {{"hashCode", "()I", reinterpret_cast<void*>(BogusMethod)}};
+    JNINativeMethod methods[] = {{"getClass", "()Ljava/lang/Class;", reinterpret_cast<void*>(BogusMethod)}};
     env_->RegisterNatives(jlobject, methods, 1);
   }
   EXPECT_FALSE(env_->ExceptionCheck());