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..34b6342c97206da6d07c3a1ffa73a2bc70c68dbf 100644
--- a/runtime/vm/debugger.h
+++ b/runtime/vm/debugger.h
@@ -352,6 +352,7 @@ class ActivationFrame : public ZoneAllocated {
                                  intptr_t var_ctx_level);
 
   intptr_t TryIndex();
+  intptr_t DeoptId();
   void GetPcDescriptors();
   void GetVarDescriptors();
   void GetDescIndices();
@@ -396,6 +397,7 @@ 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_;