Allocate a Dart_CMessage structure when decoding a message into C structures

runtime/vm/snapshot.h

Index: runtime/vm/snapshot.h
diff --git a/runtime/vm/snapshot.h b/runtime/vm/snapshot.h
index a71e8cae03560e6b52c5a206e4c06f95d09ca168..045d36f19e36101798b6898f0acb50746ab6da17 100644
--- a/runtime/vm/snapshot.h
+++ b/runtime/vm/snapshot.h
@@ -424,7 +424,7 @@ class CMessageReader : public BaseReader {
   CMessageReader(const uint8_t* buffer, intptr_t length, ReAlloc alloc);
   ~CMessageReader() { }
 
-  Dart_CObject* ReadObject();
+  Dart_CMessage* ReadMessage();
 
  private:
   // Allocates a Dart_CObject object on the C heap.
@@ -448,6 +448,7 @@ class CMessageReader : public BaseReader {
   Dart_CObject* ReadInlinedObject(intptr_t object_id);
   Dart_CObject* ReadObjectImpl(intptr_t header);
   Dart_CObject* ReadIndexedObject(intptr_t object_id);
+  Dart_CObject* ReadObject();
 
   // Add object to backward references.
   void AddBackwardReference(intptr_t id, Dart_CObject* obj);
@@ -459,9 +460,13 @@ class CMessageReader : public BaseReader {
 
   ReAlloc alloc_;
   GrowableArray<Dart_CObject*> backward_references_;
+  GrowableArray<Dart_CObject*> allocated_;
 
   Dart_CObject type_arguments_marker;
   Dart_CObject dynamic_type_marker;
+
+  const uint8_t* original_message_;
+  intptr_t original_message_length_;
 };