[Refactor Xcode Objects] Decouple file references and indexing target.

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 257 matching lines @@
 // PBXProject -----------------------------------------------------------------
 
 class PBXProject : public PBXObject {
  public:
   PBXProject(const std::string& name,
              const std::string& config_name,
              const std::string& source_path,
              const PBXAttributes& attributes);
   ~PBXProject() override;
 
+  void AddSourceFileToIndexingTarget(const std::string& navigator_path,
+                                     const std::string& source_path);
   void AddSourceFile(const std::string& navigator_path,
-                     const std::string& source_path);
+                     const std::string& source_path,
+                     PBXNativeTarget* target);
+
   void AddAggregateTarget(const std::string& name,
                           const std::string& shell_script);
+  void AddIndexingTarget();
   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);
 
   void SetProjectDirPath(const std::string& project_dir_path);
   void SetProjectRoot(const std::string& project_root);
   void AddTarget(std::unique_ptr<PBXTarget> target);
 
@@ skipping 98 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_