[debugger] keep scope and context chain for hidden scopes in sync.

src/debug/debug-scopes.h

 // Copyright 2015 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_DEBUG_DEBUG_SCOPES_H_
 #define V8_DEBUG_DEBUG_SCOPES_H_
 
 #include "src/debug/debug-frames.h"
 #include "src/frames.h"
 
@@ skipping 67 matching lines @@
 
 #ifdef DEBUG
   // Debug print of the content of the current scope.
   void DebugPrint();
 #endif
 
  private:
   struct ExtendedScopeInfo {
     ExtendedScopeInfo(Handle<ScopeInfo> info, int start, int end)
         : scope_info(info), start_position(start), end_position(end) {}
+    explicit ExtendedScopeInfo(Handle<ScopeInfo> info)
+        : scope_info(info), start_position(-1), end_position(-1) {}
     Handle<ScopeInfo> scope_info;
     int start_position;
     int end_position;
+    bool is_hidden() { return start_position == -1 && end_position == -1; }
   };
 
   Isolate* isolate_;
   FrameInspector* const frame_inspector_;
   Handle<Context> context_;
   List<ExtendedScopeInfo> nested_scope_chain_;
   Handle<StringSet> non_locals_;
   bool seen_script_scope_;
   bool failed_;
 
@@ skipping 57 matching lines @@
   void GetNestedScopeChain(Isolate* isolate, Scope* scope,
                            int statement_position);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ScopeIterator);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_DEBUG_DEBUG_SCOPES_H_