Remember deopt-id -> context-level mappings in var descriptors.

runtime/vm/debugger.h

Index: runtime/vm/debugger.h
diff --git a/runtime/vm/debugger.h b/runtime/vm/debugger.h
index d7e571e3d3c911e3ab4ec4894c1a09c61cd8c5b3..e1b23926585d29910624c6c3f7cd5e8dace5cd5d 100644
--- a/runtime/vm/debugger.h
+++ b/runtime/vm/debugger.h
@@ -350,8 +350,10 @@ class ActivationFrame : public ZoneAllocated {
   void PrintContextMismatchError(intptr_t ctx_slot,
                                  intptr_t frame_ctx_level,
                                  intptr_t var_ctx_level);
+  void PrintDescriptorsError(const char* message);
 
   intptr_t TryIndex();
+  intptr_t DeoptId();
   void GetPcDescriptors();
   void GetVarDescriptors();
   void GetDescIndices();
@@ -396,6 +398,7 @@ class ActivationFrame : public ZoneAllocated {
   bool token_pos_initialized_;
   TokenPosition token_pos_;
   intptr_t try_index_;
+  intptr_t deopt_id_;
 
   intptr_t line_number_;
   intptr_t column_number_;