Fixes a couple problems with GC of unoptimized code.

runtime/vm/block_scheduler.cc

 // Copyright (c) 2013, 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/block_scheduler.h"
 
 #include "vm/allocation.h"
 #include "vm/code_patcher.h"
 #include "vm/flow_graph.h"
 
@@ skipping 35 matching lines @@
             static_cast<double>(count) / static_cast<double>(entry_count);
         jump->set_edge_weight(weight);
       }
     }
   }
 }
 
 
 void BlockScheduler::AssignEdgeWeights() const {
   const Code& unoptimized_code = Code::Handle(
-      flow_graph()->parsed_function().function().unoptimized_code());
+      flow_graph()->parsed_function().code());
+  ASSERT(!unoptimized_code.IsNull());
 
   intptr_t entry_count =
       ComputeEdgeCount(unoptimized_code,
                        flow_graph()->graph_entry()->normal_entry()->deopt_id());
   flow_graph()->graph_entry()->set_entry_count(entry_count);
 
   for (BlockIterator it = flow_graph()->reverse_postorder_iterator();
        !it.Done();
        it.Advance()) {
     BlockEntryInstr* block = it.Current();
@@ skipping 129 matching lines @@
   for (intptr_t i = block_count - 1; i >= 0; --i) {
     if (chains[i]->first->block == flow_graph()->postorder()[i]) {
       for (Link* link = chains[i]->first; link != NULL; link = link->next) {
         flow_graph()->CodegenBlockOrder(true)->Add(link->block);
       }
     }
   }
 }
 
 }  // namespace dart