Add IR printing into a supplied buffer.

vm/flow_graph_compiler_x64.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_FLOW_GRAPH_COMPILER_X64_H_
 #define VM_FLOW_GRAPH_COMPILER_X64_H_
 
 #ifndef VM_FLOW_GRAPH_COMPILER_H_
 #error Include flow_graph_compiler.h instead of flow_graph_compiler_x64.h.
 #endif
@@ skipping 62 matching lines @@
 
   FOR_EACH_COMPUTATION(DECLARE_VISIT_COMPUTATION)
   FOR_EACH_INSTRUCTION(DECLARE_VISIT_INSTRUCTION)
 
 #undef DECLARE_VISIT_COMPUTATION
 #undef DECLARE_VISIT_INSTRUCTION
 
   // Emit code to load a Value into register 'dst'.
   void LoadValue(Register dst, Value* value);
 
+  void EmitComment(Instruction* instr);
+
   // Emit an instance call.
   void EmitInstanceCall(intptr_t cid,
                         intptr_t token_index,
                         intptr_t try_index,
                         const String& function_name,
                         intptr_t argument_count,
                         const Array& argument_names,
                         intptr_t checked_argument_count);
 
   // Emit a static call.
@@ skipping 53 matching lines @@
   DescriptorList* pc_descriptors_list_;
   ExceptionHandlerList* exception_handlers_list_;
   const bool is_optimizing_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_COMPILER_X64_H_