[debugger] correctly find function context.

src/contexts.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CONTEXTS_H_
 #define V8_CONTEXTS_H_
 
 #include "src/heap/heap.h"
 #include "src/objects.h"
 
@@ skipping 432 matching lines @@
   String* catch_name();
 
   inline JSModule* module();
   inline void set_module(JSModule* module);
 
   // Get the context where var declarations will be hoisted to, which
   // may be the context itself.
   Context* declaration_context();
   bool is_declaration_context();
 
+  // Get the next closure's context on the context chain.
+  Context* closure_context();
+
   // Returns a JSGlobalProxy object or null.
   JSObject* global_proxy();
   void set_global_proxy(JSObject* global);
 
   // Get the JSGlobalObject object.
   JSGlobalObject* global_object();
 
   // Get the script context by traversing the context chain.
   Context* script_context();
 
@@ skipping 123 matching lines @@
 #endif
 
   STATIC_ASSERT(kHeaderSize == Internals::kContextHeaderSize);
   STATIC_ASSERT(EMBEDDER_DATA_INDEX == Internals::kContextEmbedderDataIndex);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CONTEXTS_H_