Attempt to fix dart2js crashes

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
diff --git a/runtime/vm/flow_graph_optimizer.cc b/runtime/vm/flow_graph_optimizer.cc
index e9420e8dffde5c9a9de4496652fcc7c84536d0a5..564b58ff90558111dadd84441bec00ce71d1d65d 100644
--- a/runtime/vm/flow_graph_optimizer.cc
+++ b/runtime/vm/flow_graph_optimizer.cc
@@ -4619,8 +4619,12 @@ void FlowGraphOptimizer::VisitStoreInstanceField(
         }
       }
       field.set_is_unboxing_candidate(false);
-      // Delay deoptimization of dependent code to the code installation time.
-      flow_graph()->deoptimize_dependent_code().Add(&field);
+      if (Compiler::IsBackgroundCompilation()) {
+        // Delay deoptimization of dependent code to the code installation time.
+        flow_graph()->deoptimize_dependent_code().Add(&field);
+      } else {
+        field.DeoptimizeDependentCode();
+      }
     } else {
       FlowGraph::AddToGuardedFields(flow_graph_->guarded_fields(), &field);
     }