Fixes a problem with the recovery of contexts in the debugger at closure calls.

runtime/vm/debugger.h

Index: runtime/vm/debugger.h
diff --git a/runtime/vm/debugger.h b/runtime/vm/debugger.h
index 0664bac4222dbacf7df2c1b4f2237dde4cda850f..74546e3c39e4e15bdb2645abae1d60b5f2803f7e 100644
--- a/runtime/vm/debugger.h
+++ b/runtime/vm/debugger.h
@@ -177,6 +177,11 @@ class ActivationFrame : public ZoneAllocated {
   void PrintToJSONObject(JSONObject* jsobj);
 
  private:
+  void PrintContextMismatchError(const String& var_name,
+                                 intptr_t ctx_slot,
+                                 intptr_t frame_ctx_level,
+                                 intptr_t var_ctx_level);
+
   intptr_t PcDescIndex();
   intptr_t TryIndex();
   void GetPcDescriptors();