Allocate a Dart_CMessage structure when decoding a message into C structures

runtime/vm/snapshot.cc

Index: runtime/vm/snapshot.cc
diff --git a/runtime/vm/snapshot.cc b/runtime/vm/snapshot.cc
index 472a2d20766dcbef85c3b041d7bce0d33d167601..78fe6a70d2f910f8ec6c74c601e35cd268f996ad 100644
--- a/runtime/vm/snapshot.cc
+++ b/runtime/vm/snapshot.cc
@@ -455,6 +455,17 @@ CMessageReader::CMessageReader(const uint8_t* buffer,
 }
 
 
+Dart_CMessage* CMessageReader::ReadMessage() {
+  // Read the object out of the message.
+  Dart_CObject* object = ReadObject();
+
+  Dart_CMessage* message =
+      reinterpret_cast<Dart_CMessage*>(alloc_(NULL, 0, sizeof(Dart_CMessage)));
+  if (message == NULL) return NULL;
+  message->root = object;
+  return message;
+}
+
 intptr_t CMessageReader::LookupInternalClass(intptr_t class_header) {
   SerializedHeaderType header_type = SerializedHeaderTag::decode(class_header);
   ASSERT(header_type == kObjectId);