Print field info on mark sweep invalid ref crash.

(cherry pick commit eb2baaf20d9059c0fc38141780ec05bea0486c40)

Bug: 20557050
Change-Id: I3abb7a44e3b7ed3256653824fd1705aac5f7d72c
diff --git a/runtime/mirror/object.cc b/runtime/mirror/object.cc
index 5dac985..f9740bb 100644
--- a/runtime/mirror/object.cc
+++ b/runtime/mirror/object.cc
@@ -244,5 +244,10 @@
   UNREACHABLE();
 }
 
+ArtField* Object::FindFieldByOffset(MemberOffset offset) {
+  return IsClass() ? ArtField::FindStaticFieldWithOffset(AsClass(), offset.Uint32Value())
+      : ArtField::FindInstanceFieldWithOffset(GetClass(), offset.Uint32Value());
+}
+
 }  // namespace mirror
 }  // namespace art