ART: Refactor jfieldID handling

ArtField objects have been native since Marshmallow.
Remove the dependency on being runnable. Refactor the
code into the jni_internal header.

Test: m test-art-host
Change-Id: I46708c70f9b4b566d7e26e4c5ffc3f0cbadc43fa
diff --git a/runtime/thread.h b/runtime/thread.h
index 4f26803..f3001be 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -333,8 +333,7 @@
   }
 
   // Returns the java.lang.Thread's name, or null if this Thread* doesn't have a peer.
-  mirror::String* GetThreadName(const ScopedObjectAccessAlreadyRunnable& ts) const
-      REQUIRES_SHARED(Locks::mutator_lock_);
+  mirror::String* GetThreadName() const REQUIRES_SHARED(Locks::mutator_lock_);
 
   // Sets 'name' to the java.lang.Thread's name. This requires no transition to managed code,
   // allocation, or locking.