Clean up VM class DartFunction.

runtime/vm/raw_object_snapshot.cc

Index: runtime/vm/raw_object_snapshot.cc
===================================================================
--- runtime/vm/raw_object_snapshot.cc	(revision 26047)
+++ runtime/vm/raw_object_snapshot.cc	(working copy)
@@ -48,7 +48,7 @@
       cls = reader->NewClass(class_id);
     } else {
       if (class_id < kNumPredefinedCids) {
-        ASSERT((class_id >= kInstanceCid) && (class_id <= kDartFunctionCid));
+        ASSERT((class_id >= kInstanceCid) && (class_id <= kMirrorReferenceCid));
         cls = reader->isolate()->class_table()->At(class_id);
       } else {
         cls = New<Instance>(kIllegalCid);
@@ -2473,22 +2473,6 @@
 #undef EXT_TYPED_DATA_WRITE
 
 
-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.
-}
-
-
 RawStacktrace* Stacktrace::ReadFrom(SnapshotReader* reader,
                                     intptr_t object_id,
                                     intptr_t tags,