[Refactor Xcode Objects] Allow extra attributes for native targets.

tools/gn/xcode_object.h

 // Copyright 2016 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_XCODE_OBJECT_H_
 #define TOOLS_GN_XCODE_OBJECT_H_
 
 #include <iosfwd>
 #include <map>
 #include <memory>
@@ skipping 266 matching lines @@
 
   void AddSourceFileToIndexingTarget(const std::string& navigator_path,
                                      const std::string& source_path);
   void AddSourceFile(const std::string& navigator_path,
                      const std::string& source_path,
                      PBXNativeTarget* target);
 
   void AddAggregateTarget(const std::string& name,
                           const std::string& shell_script);
   void AddIndexingTarget();
+
+  // NOTE: |extra_attributes| values may be overridden within this function.

[sdefresne, 2016/12/21 09:39:12]

I understand what you mean by this comment, but only after reading the code.
I've tried to think of better comments (things like "Attributes from
|extra_attributes| may be ignored.") but nothing that meant the code clearer to
understand. In fact, I find it easier to understand without the comment (as I
then think "oh, they are extra attributes, so I can only set things that are not
already set inside the function).

WDYT about just removing this comment?

[liaoyuke, 2016/12/21 16:59:26]

Make sense. The "extra" in the name should explain everything.

   void AddNativeTarget(const std::string& name,
                        const std::string& type,
                        const std::string& output_name,
                        const std::string& output_type,
-                       const std::string& shell_script);
+                       const std::string& shell_script,
+                       const PBXAttributes& extra_attributes = PBXAttributes());
 
   void SetProjectDirPath(const std::string& project_dir_path);
   void SetProjectRoot(const std::string& project_root);
   void AddTarget(std::unique_ptr<PBXTarget> target);
 
   // PBXObject implementation.
   PBXObjectClass Class() const override;
   std::string Name() const override;
   std::string Comment() const override;
   void Visit(PBXObjectVisitor& visitor) override;
@@ skipping 93 matching lines @@
   void Print(std::ostream& out, unsigned indent) const override;
 
  private:
   std::vector<std::unique_ptr<XCBuildConfiguration>> configurations_;
   const PBXObject* owner_reference_;
 
   DISALLOW_COPY_AND_ASSIGN(XCConfigurationList);
 };
 
 #endif  // TOOLS_GN_XCODE_OBJECT_H_