Lazy deopt:

runtime/vm/stack_frame.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/stack_frame.h"
 
 #include "platform/memory_sanitizer.h"
 #include "vm/assembler.h"
 #include "vm/deopt_instructions.h"
 #include "vm/isolate.h"
@@ skipping 548 matching lines @@
 #else
       return (index - num_materializations_);
 #endif
     }
   }
   UNREACHABLE();
   return 0;
 }
 
 
+#if defined(DEBUG)
+void ValidateFrames() {
+  StackFrameIterator frames(StackFrameIterator::kValidateFrames);
+  StackFrame* frame = frames.NextFrame();
+  while (frame != NULL) {
+    frame = frames.NextFrame();
+  }
+}
+#endif
+
+
 }  // namespace dart