Background compilation work:

runtime/vm/flow_graph_optimizer.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/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
 #include "vm/cpu.h"
@@ skipping 4601 matching lines @@
       if (FLAG_trace_optimization || FLAG_trace_field_guards) {
         THR_Print("Disabling unboxing of %s\n", field.ToCString());
         if (!setter.IsNull()) {
           OS::Print("  setter usage count: %" Pd "\n", setter.usage_counter());
         }
         if (!getter.IsNull()) {
           OS::Print("  getter usage count: %" Pd "\n", getter.usage_counter());
         }
       }
       field.set_is_unboxing_candidate(false);
-      field.DeoptimizeDependentCode();
+      // Delay deoptimization of dependent code to the code installation time.
+      flow_graph()->deoptimize_dependent_code().Add(&field);
     } else {
       FlowGraph::AddToGuardedFields(flow_graph_->guarded_fields(), &field);
     }
   }
 }
 
 
 void FlowGraphOptimizer::VisitAllocateContext(AllocateContextInstr* instr) {
   // Replace generic allocation with a sequence of inlined allocation and
   // explicit initalizing stores.
@@ skipping 4149 matching lines @@
 
   // Insert materializations at environment uses.
   for (intptr_t i = 0; i < exits_collector_.exits().length(); i++) {
     CreateMaterializationAt(
         exits_collector_.exits()[i], alloc, *slots);
   }
 }
 
 
 }  // namespace dart