Avoid trusting the length encoded in the Snapshot if there is an

runtime/vm/dart_api_message.h

Index: runtime/vm/dart_api_message.h
===================================================================
--- runtime/vm/dart_api_message.h	(revision 10993)
+++ runtime/vm/dart_api_message.h	(working copy)
@@ -124,12 +124,9 @@
   // Writes a message of integers.
   void WriteMessage(intptr_t field_count, intptr_t *data);
 
+  // Writes a message with a single object.
   void WriteCMessage(Dart_CObject* object);
 
-  void FinalizeBuffer() {
-    BaseWriter::FinalizeBuffer(Snapshot::kMessage);
-  }
-
  private:
   static const intptr_t kDartCObjectTypeBits = 4;
   static const intptr_t kDartCObjectTypeMask = (1 << kDartCObjectTypeBits) - 1;