Add --print-flow-graph-filter to allow filtering debugging output.

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"
 #include "vm/growable_array.h"
 #include "vm/object_store.h"
 #include "vm/report.h"
 
 namespace dart {
 
 DEFINE_FLAG(bool, prune_dead_locals, true, "optimize dead locals away");
 DECLARE_FLAG(bool, reorder_basic_blocks);
 DECLARE_FLAG(bool, trace_optimization);
@@ skipping 1363 matching lines @@
 }
 
 
 bool BlockEffects::IsSideEffectFreePath(BlockEntryInstr* from,
                                         BlockEntryInstr* to) const {
   return available_at_[to->postorder_number()]->Contains(
       from->postorder_number());
 }
 
 }  // namespace dart