Partially implement DBC profiler.

runtime/vm/simulator_arm64.h

 // Copyright (c) 2014, 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.
 
 // Declares a Simulator for ARM64 instructions if we are not generating a native
 // ARM64 binary. This Simulator allows us to run and debug ARM64 code generation
 // on regular desktop machines.
 // Dart calls into generated code by "calling" the InvokeDartCode stub,
 // which will start execution in the Simulator or forwards to the real entry
 // on a ARM64 HW platform.
@@ skipping 62 matching lines @@
   int64_t get_last_pc() const;
   void set_pc(int64_t pc);
 
   // Accessors to the internal simulator stack base and top.
   uword StackBase() const { return reinterpret_cast<uword>(stack_); }
   uword StackTop() const;
 
   // Accessor to the instruction counter.
   uint64_t get_icount() const { return icount_; }
 
-  // The isolate's top_exit_frame_info refers to a Dart frame in the simulator
+  // The thread's top_exit_frame_info refers to a Dart frame in the simulator
   // stack. The simulator's top_exit_frame_info refers to a C++ frame in the
   // native stack.
   uword top_exit_frame_info() const { return top_exit_frame_info_; }
   void set_top_exit_frame_info(uword value) { top_exit_frame_info_ = value; }
 
   // Call on program start.
   static void InitOnce();
 
   // Dart generally calls into generated code with 4 parameters. This is a
   // convenience function, which sets up the simulator state and grabs the
@@ skipping 182 matching lines @@
   }
 
   friend class SimulatorDebugger;
   friend class SimulatorSetjmpBuffer;
   DISALLOW_COPY_AND_ASSIGN(Simulator);
 };
 
 }  // namespace dart
 
 #endif  // VM_SIMULATOR_ARM64_H_