Support for excluding variable from forwarding via forward_variables_form.

tools/gn/scope.h

 // Copyright (c) 2013 The Chromium 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 TOOLS_GN_SCOPE_H_
 #define TOOLS_GN_SCOPE_H_
 
 #include <map>
 #include <set>
 #include <utility>
@@ skipping 47 matching lines @@
     // generated, or NULL if there is none.
     virtual const Value* GetProgrammaticValue(
         const base::StringPiece& ident) = 0;
 
    protected:
     Scope* scope_;
   };
 
   // Options for configuring scope merges.
   struct MergeOptions {
-    // Defaults to all false, which are the things least likely to cause errors.
-    MergeOptions()
-        : clobber_existing(false),
-          skip_private_vars(false),
-          mark_dest_used(false) {
-    }
+    MergeOptions();
+    ~MergeOptions();
 
     // When set, all existing avlues in the destination scope will be
     // overwritten.
     //
     // When false, it will be an error to merge a variable into another scope
     // where a variable with the same name is already set. The exception is
     // if both of the variables have the same value (which happens if you
     // somehow multiply import the same file, for example). This case will be
     // ignored since there is nothing getting lost.
     bool clobber_existing;
 
     // When true, private variables (names beginning with an underscore) will
     // be copied to the destination scope. When false, private values will be
     // skipped.
     bool skip_private_vars;
 
     // When set, values copied to the destination scope will be marked as used
     // so won't trigger an unused variable warning. You want this when doing an
     // import, for example, or files that don't need a variable from the .gni
     // file will throw an error.
     bool mark_dest_used;
+
+    // When set, those variables are not merged.
+    std::set<std::string> excluded_values;
   };
 
   // Creates an empty toplevel scope.
   explicit Scope(const Settings* settings);
 
   // Creates a dependent scope.
   explicit Scope(Scope* parent);
   explicit Scope(const Scope* parent);
 
   ~Scope();
@@ skipping 250 matching lines @@
 
   typedef std::set<ProgrammaticProvider*> ProviderSet;
   ProviderSet programmatic_providers_;
 
   SourceDir source_dir_;
 
   DISALLOW_COPY_AND_ASSIGN(Scope);
 };
 
 #endif  // TOOLS_GN_SCOPE_H_