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

src/debug/debug-scopes.cc

 // 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.
 
 #include "src/debug/debug-scopes.h"
 
 #include "src/ast/scopes.h"
 #include "src/debug/debug.h"
 #include "src/frames-inl.h"
 #include "src/globals.h"
@@ skipping 183 matching lines @@
     if (!nested_scope_chain_.is_empty()) {
       DCHECK_EQ(nested_scope_chain_.last().scope_info->scope_type(),
                 SCRIPT_SCOPE);
       nested_scope_chain_.RemoveLast();
       DCHECK(nested_scope_chain_.is_empty());
     }
     CHECK(context_->IsNativeContext());
   } else if (nested_scope_chain_.is_empty()) {
     context_ = Handle<Context>(context_->previous(), isolate_);
   } else {
-    if (nested_scope_chain_.last().scope_info->HasContext()) {
-      DCHECK(context_->previous() != NULL);
-      context_ = Handle<Context>(context_->previous(), isolate_);
-    }
-    nested_scope_chain_.RemoveLast();
+    do {
+      if (nested_scope_chain_.last().scope_info->HasContext()) {
+        DCHECK(context_->previous() != NULL);
+        context_ = Handle<Context>(context_->previous(), isolate_);
+      }
+      nested_scope_chain_.RemoveLast();
+      if (nested_scope_chain_.is_empty()) break;
+      // Repeat to skip hidden scopes.
+    } while (nested_scope_chain_.last().is_hidden());
   }
   UnwrapEvaluationContext();
 }
 
 
 // Return the type of the current scope.
 ScopeIterator::ScopeType ScopeIterator::Type() {
   DCHECK(!failed_);
   if (!nested_scope_chain_.is_empty()) {
     Handle<ScopeInfo> scope_info = nested_scope_chain_.last().scope_info;
@@ skipping 570 matching lines @@
         isolate_, value, Object::GetPropertyOrElement(extension, key), false);
     RETURN_ON_EXCEPTION_VALUE(
         isolate_, JSObject::SetOwnPropertyIgnoreAttributes(
             scope_object, key, value, NONE), false);
   }
   return true;
 }
 
 void ScopeIterator::GetNestedScopeChain(Isolate* isolate, Scope* scope,
                                         int position) {
-  if (!scope->is_eval_scope() && !scope->is_hidden()) {
-    nested_scope_chain_.Add(ExtendedScopeInfo(scope->GetScopeInfo(isolate),
-                                              scope->start_position(),
-                                              scope->end_position()));
+  if (!scope->is_eval_scope()) {
+    if (scope->is_hidden()) {
+      // We need to add this chain element in case the scope has a context
+      // associated. We need to keep the scope chain and context chain in sync.
+      nested_scope_chain_.Add(ExtendedScopeInfo(scope->GetScopeInfo(isolate)));
+    } else {
+      nested_scope_chain_.Add(ExtendedScopeInfo(scope->GetScopeInfo(isolate),
+                                                scope->start_position(),
+                                                scope->end_position()));
+    }
   }
   for (int i = 0; i < scope->inner_scopes()->length(); i++) {
     Scope* inner_scope = scope->inner_scopes()->at(i);
     int beg_pos = inner_scope->start_position();
     int end_pos = inner_scope->end_position();
     DCHECK((beg_pos >= 0 && end_pos >= 0) || inner_scope->is_hidden());
     if (beg_pos <= position && position < end_pos) {
       GetNestedScopeChain(isolate, inner_scope, position);
       return;
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8