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

runtime/vm/il_printer.h

 // 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.
 
 #ifndef VM_IL_PRINTER_H_
 #define VM_IL_PRINTER_H_
 
 #include "vm/flow_graph.h"
 #include "vm/intermediate_language.h"
 
@@ skipping 42 matching lines @@
                              const AbstractType& dst_type,
                              const String& dst_name,
                              bool eliminated);
   static void PrintBlock(BlockEntryInstr* block, bool print_locations);
 
   static void PrintGraph(const char* phase, FlowGraph* flow_graph);
 
   // Debugging helper function.
   static void PrintICData(const ICData& ic_data);
 
+  static bool ShouldPrint(const Function& function);
+
+  static bool PassesFilter(const char* filter, const Function& function);
+
  private:
   const Function& function_;
   const GrowableArray<BlockEntryInstr*>& block_order_;
   const bool print_locations_;
 };
 
 }  // namespace dart
 
 #endif  // VM_IL_PRINTER_H_