Implement Dart VM option '--trace_sim_after' in DBC simulator

runtime/vm/simulator_dbc.h

Index: runtime/vm/simulator_dbc.h
diff --git a/runtime/vm/simulator_dbc.h b/runtime/vm/simulator_dbc.h
index 2e84f9844c932935cd9fd757470b825fa5619b6b..a683ba6e97e7dc6d083519b45e8a5ea1af26f5db 100644
--- a/runtime/vm/simulator_dbc.h
+++ b/runtime/vm/simulator_dbc.h
@@ -93,6 +93,7 @@ class Simulator {
 
   RawObject** fp_;
   uword pc_;
+  uint64_t icount_;

[zra, 2017/06/30 18:59:14]

We don't need this field in a PRODUCT build. You can exclude it with:

NOT_IN_PRODUCT(uint64_t icount_);

[alexmarkov, 2017/06/30 23:02:00]

Done.

 
   SimulatorSetjmpBuffer* last_setjmp_buffer_;
   uword top_exit_frame_info_;
@@ -161,6 +162,12 @@ class Simulator {
                      RawObject*** SP,
                      bool optimized);
 
+  // Returns true if tracing of executed instructions is enabled.
+  bool IsTracingExecution() const;

[zra, 2017/06/30 18:59:14]

ditto

[alexmarkov, 2017/06/30 23:01:59]

Done.

+
+  // Prints bytecode instruction at given pc for instruction tracing.
+  void TraceInstruction(uint32_t* pc) const;

[zra, 2017/06/30 18:59:14]

ditto

[alexmarkov, 2017/06/30 23:01:59]

Done.

+
   // Longjmp support for exceptions.
   SimulatorSetjmpBuffer* last_setjmp_buffer() { return last_setjmp_buffer_; }
   void set_last_setjmp_buffer(SimulatorSetjmpBuffer* buffer) {