Fixes bug where we would occasionally materialize a corrupted object.

runtime/vm/il_printer.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/il_printer.h"
 
 #include "vm/intermediate_language.h"
 #include "vm/os.h"
 #include "vm/parser.h"
 
@@ skipping 1039 matching lines @@
     if ((locations_ != NULL) && !locations_[i].IsInvalid()) {
       f->Print(" [");
       locations_[i].PrintTo(f);
       f->Print("]");
     }
   }
   f->Print(" }");
   if (outer_ != NULL) outer_->PrintTo(f);
 }
 
+const char* Environment::ToCString() const {
+  char buffer[1024];
+  BufferFormatter bf(buffer, 1024);
+  PrintTo(&bf);
+  return Isolate::Current()->current_zone()->MakeCopyOfString(buffer);
+}
+
 }  // namespace dart