[GN] Add support for generating Xcode projects.

tools/gn/xcode_writer.h

Index: tools/gn/xcode_writer.h
diff --git a/tools/gn/xcode_writer.h b/tools/gn/xcode_writer.h
new file mode 100644
index 0000000000000000000000000000000000000000..0a11dde0403c7f8560dedeb01239aa993b9603fb
--- /dev/null
+++ b/tools/gn/xcode_writer.h
@@ -0,0 +1,90 @@
+// 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_WRITER_H_
+#define TOOLS_GN_XCODE_WRITER_H_
+
+#include <iosfwd>
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+
+class Builder;
+class BuildSettings;
+class Err;
+class SourceDir;
+class Target;
+
+using PBXAttributes = std::map<std::string, std::string>;
+class PBXProject;
+
+class XcodeWriter {
+ public:
+  enum TargetOsType {
+    WRITER_TARGET_OS_IOS,
+    WRITER_TARGET_OS_MACOS,
+  };
+
+  // Writes Xcode workspace and project files.
+  //
+  // |workspace_name| is the optional name of the workspace file name ("all"
+  // is used if not specified). |root_target_name| is the name of the main
+  // target corresponding to building "All" (for example "gn_all" in Chromium).
+  // |ninja_extra_args| are additional arguments to pass to ninja invocation
+  // (can be used to increase limit of concurrent processes when using goma).
+  // |target_filter_pattern| is a regular expression used to filter the targets
+  // to generate. If not set, all targets are present in the generated project.
+  //
+  // On failure will populate |err| and return false.
+  static bool RunAndWriteFiles(const std::string& workspace_name,
+                               const std::string& root_target_name,
+                               const std::string& ninja_extra_args,
+                               const std::string& target_filter_pattern,
+                               const BuildSettings* build_settings,
+                               Builder* builder,
+                               Err* err);
+
+ private:
+  XcodeWriter(const std::string& name);
+  ~XcodeWriter();
+
+  static std::vector<const Target*> FilterTargets(
+      const std::vector<const Target*>& all_targets,
+      const std::string& target_filter_pattern);
+
+  void CreateMainProject(const std::vector<const Target*>& targets,
+                         const PBXAttributes& attributes,
+                         const std::string& project_name,
+                         const std::string& source_path,
+                         const std::string& config_name,
+                         const std::string& root_target,
+                         const std::string& ninja_extra_args,
+                         const std::string& target_filter_pattern,
+                         TargetOsType target_os);
+
+  void CreateSourceForIndexingProject(const std::vector<const Target*>& targets,
+                                      const SourceDir& root_build_dir,
+                                      const PBXAttributes& attributes,
+                                      const std::string& project_name,
+                                      const std::string& source_path,
+                                      const std::string& config_name,
+                                      TargetOsType target_os);
+
+  bool WriteFiles(const BuildSettings* build_settings, Err* err);
+  bool WriteProjectFile(const BuildSettings* build_settings,
+                        PBXProject* project,
+                        Err* err);
+
+  void WriteWorkspaceContent(std::ostream& out);
+  void WriteProjectContent(std::ostream& out, PBXProject* project);
+
+  std::string name_;
+  std::vector<std::unique_ptr<PBXProject>> projects_;
+
+  DISALLOW_COPY_AND_ASSIGN(XcodeWriter);
+};
+
+#endif  // TOOLS_GN_XCODE_WRITER_H_