Wire GrowableArray to use the internal VM object.

vm/raw_object_snapshot.cc

Index: vm/raw_object_snapshot.cc
===================================================================
--- vm/raw_object_snapshot.cc	(revision 6332)
+++ vm/raw_object_snapshot.cc	(working copy)
@@ -1752,7 +1752,12 @@
 
   // Read the length so that we can determine instance size to allocate.
   GrowableObjectArray& array = GrowableObjectArray::ZoneHandle(
-      reader->isolate(), reader->NewGrowableObjectArray());
+      reader->isolate(), GrowableObjectArray::null());
+  if (kind == Snapshot::kFull) {
+    array = reader->NewGrowableObjectArray();
+  } else {
+    array = GrowableObjectArray::New(0);
+  }
   reader->AddBackwardReference(object_id, &array);
   intptr_t length = reader->ReadSmiValue();
   array.SetLength(length);