Partially implement DBC profiler.

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 2cbadce6a11247269b1212849c376399a5e32295..bb875bbd79b0ad859415d1d7c3158529d216cdf1 100644
--- a/runtime/vm/simulator_dbc.h
+++ b/runtime/vm/simulator_dbc.h
@@ -50,7 +50,7 @@ class Simulator {
   uword StackBase() const { return reinterpret_cast<uword>(stack_); }
   uword StackTop() const;
 
-  // 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_; }
@@ -71,9 +71,9 @@ class Simulator {
                RawObject* raw_stacktrace,
                Thread* thread);
 
-  uword get_sp() const {
-    return reinterpret_cast<uword>(sp_);
-  }
+  uword get_sp() const { return reinterpret_cast<uword>(sp_); }
+  uword get_fp() const { return reinterpret_cast<uword>(fp_); }
+  uword get_pc() const { return reinterpret_cast<uword>(pc_); }
 
   enum IntrinsicId {
 #define V(test_class_name, test_function_name, enum_name, type, fp) \