[debugger] do not expose temporary variables introduced by the parser.

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 783 matching lines @@
 }
 
 
 void ScopeIterator::CopyContextLocalsToScopeObject(
     Handle<ScopeInfo> scope_info, Handle<Context> context,
     Handle<JSObject> scope_object) {
   Isolate* isolate = scope_info->GetIsolate();
   int local_count = scope_info->ContextLocalCount();
   if (local_count == 0) return;
   // Fill all context locals to the context extension.
-  int first_context_var = scope_info->StackLocalCount();
-  int start = scope_info->ContextLocalNameEntriesIndex();
   for (int i = 0; i < local_count; ++i) {
-    if (scope_info->LocalIsSynthetic(first_context_var + i)) continue;
+    Handle<String> name(scope_info->ContextLocalName(i));
+    if (ScopeInfo::VariableIsSynthetic(*name)) continue;
     int context_index = Context::MIN_CONTEXT_SLOTS + i;
     Handle<Object> value = Handle<Object>(context->get(context_index), isolate);
     // Reflect variables under TDZ as undefined in scope object.
     if (value->IsTheHole()) continue;
     // This should always succeed.
     // TODO(verwaest): Use AddDataProperty instead.
-    JSObject::SetOwnPropertyIgnoreAttributes(
-        scope_object, handle(String::cast(scope_info->get(i + start))), value,
-        NONE)
+    JSObject::SetOwnPropertyIgnoreAttributes(scope_object, name, value, NONE)
         .Check();
   }
 }
 
 bool ScopeIterator::CopyContextExtensionToScopeObject(
     Handle<JSObject> extension, Handle<JSObject> scope_object,
     KeyCollectionType type) {
   Handle<FixedArray> keys;
   ASSIGN_RETURN_ON_EXCEPTION_VALUE(
       isolate_, keys, JSReceiver::GetKeys(extension, type, ENUMERABLE_STRINGS),
@@ skipping 27 matching lines @@
     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