Gentle start with removing explicit interfaces

runtime/vm/raw_object_snapshot.cc

Index: runtime/vm/raw_object_snapshot.cc
===================================================================
--- runtime/vm/raw_object_snapshot.cc	(revision 11241)
+++ runtime/vm/raw_object_snapshot.cc	(working copy)
@@ -42,7 +42,7 @@
       cls = reader->NewClass(class_id, is_signature_class);
     } else {
       if (class_id < kNumPredefinedCids) {
-        ASSERT((class_id >= kInstanceCid) && (class_id <= kWeakPropertyCid));
+        ASSERT((class_id >= kInstanceCid) && (class_id <= kDartFunctionCid));
         cls = reader->isolate()->class_table()->At(class_id);
       } else {
         if (is_signature_class) {
@@ -2029,6 +2029,22 @@
 #undef BYTEARRAY_TYPE_LIST
 
 
+RawDartFunction* DartFunction::ReadFrom(SnapshotReader* reader,
+                                        intptr_t object_id,
+                                        intptr_t tags,
+                                        Snapshot::Kind kind) {
+  UNREACHABLE();  // DartFunction is an abstract class.
+  return DartFunction::null();
+}
+
+
+void RawDartFunction::WriteTo(SnapshotWriter* writer,
+                              intptr_t object_id,
+                              Snapshot::Kind kind) {
+  UNREACHABLE();  // DartFunction is an abstract class.
+}
+
+
 RawClosure* Closure::ReadFrom(SnapshotReader* reader,
                               intptr_t object_id,
                               intptr_t tags,