Fix JNI GetSuperClasss

Change-Id: I005e9f84220dabfcea7cbc7b7b0ad422dd435a40
diff --git a/runtime/mirror/class.h b/runtime/mirror/class.h
index ba8a693..551e7e2 100644
--- a/runtime/mirror/class.h
+++ b/runtime/mirror/class.h
@@ -1207,7 +1207,12 @@
   // Descriptor for the class such as "java.lang.Class" or "[C". Lazily initialized by ComputeName
   HeapReference<String> name_;
 
-  // The superclass, or null if this is java.lang.Object, an interface or primitive type.
+  // The superclass, or null if this is java.lang.Object or a primitive type.
+  //
+  // Note that interfaces have java.lang.Object as their
+  // superclass. This doesn't match the expectations in JNI
+  // GetSuperClass or java.lang.Class.getSuperClass() which need to
+  // check for interfaces and return null.
   HeapReference<Class> super_class_;
 
   // If class verify fails, we must return same error on subsequent tries.