GN: Use path service to find executable path

tools/gn/ninja_build_writer.cc

 // 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.
 
 #include "tools/gn/ninja_build_writer.h"
 
 #include <fstream>
 
 #include "base/command_line.h"
 #include "base/file_util.h"
+#include "base/path_service.h"
 #include "base/process/process_handle.h"
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
 #include "tools/gn/build_settings.h"
 #include "tools/gn/escape.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/input_file_manager.h"
 #include "tools/gn/scheduler.h"
 #include "tools/gn/target.h"
 #include "tools/gn/trace.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
 namespace {
 
 std::string GetSelfInvocationCommand(const BuildSettings* build_settings) {
-#if defined(OS_WIN)
-  wchar_t module[MAX_PATH];
-  GetModuleFileName(NULL, module, MAX_PATH);
-  //result = "\"" + base::WideToUTF8(module) + "\"";
-  base::FilePath executable(module);
-#elif defined(OS_MACOSX)
-  // FIXME(brettw) write this on Mac!
-  base::FilePath executable("../Debug/gn");
-#else
-  base::FilePath executable =
-      base::GetProcessExecutablePath(base::GetCurrentProcessHandle());
-#endif
-
-/*
-  // Append the root path.
-  CommandLine* cmdline = CommandLine::ForCurrentProcess();
-  result += " --root=\"" + FilePathToUTF8(settings->root_path()) + "\"";
-*/
+  base::FilePath executable;
+  PathService::Get(base::FILE_EXE, &executable);
 
   CommandLine cmdline(executable);
   cmdline.AppendSwitchPath("--root", build_settings->root_path());
   cmdline.AppendSwitch("-q");  // Don't write output.
 
   EscapeOptions escape_shell;
   escape_shell.mode = ESCAPE_SHELL;
 #if defined(OS_WIN)
   // The command line code quoting varies by platform. We have one string,
   // possibly with spaces, that we want to quote. The Windows command line
@@ skipping 148 matching lines @@
       all_rules.append(" $\n    ");
     all_rules.append(target_file.value());
   }
 
   if (!all_rules.empty()) {
     out_ << "\nbuild all: phony " << all_rules << std::endl;
     out_ << "default all" << std::endl;
   }
 }