ART: Move JNI files to runtime/jni/ .

Test: Rely on TreeHugger.
Change-Id: I9cae11191ef1567ae9453be498882a7767285140
diff --git a/runtime/native/java_lang_StringFactory.cc b/runtime/native/java_lang_StringFactory.cc
index 136a02f..07e875e 100644
--- a/runtime/native/java_lang_StringFactory.cc
+++ b/runtime/native/java_lang_StringFactory.cc
@@ -17,7 +17,7 @@
 #include "java_lang_StringFactory.h"
 
 #include "common_throws.h"
-#include "jni_internal.h"
+#include "jni/jni_internal.h"
 #include "mirror/object-inl.h"
 #include "mirror/string.h"
 #include "native_util.h"