Disable reg-exp compilation in background via a flag

runtime/vm/flow_graph.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/flow_graph.h"
 
 #include "vm/bit_vector.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/il_printer.h"
 #include "vm/intermediate_language.h"
@@ skipping 26 matching lines @@
     reverse_postorder_(),
     optimized_block_order_(),
     constant_null_(NULL),
     constant_dead_(NULL),
     constant_empty_context_(NULL),
     block_effects_(NULL),
     licm_allowed_(true),
     loop_headers_(NULL),
     loop_invariant_loads_(NULL),
     guarded_fields_(parsed_function.guarded_fields()),
-    deoptimize_dependent_code_(),
     deferred_prefixes_(parsed_function.deferred_prefixes()),
     captured_parameters_(new(zone()) BitVector(zone(), variable_count())),
     inlining_id_(-1) {
   DiscoverBlocks();
 }
 
 
 void FlowGraph::EnsureSSATempIndex(Definition* defn,
                                    Definition* replacement) {
   if ((replacement->ssa_temp_index() == -1) &&
@@ skipping 1370 matching lines @@
 }
 
 
 bool BlockEffects::IsSideEffectFreePath(BlockEntryInstr* from,
                                         BlockEntryInstr* to) const {
   return available_at_[to->postorder_number()]->Contains(
       from->postorder_number());
 }
 
 }  // namespace dart