Add basic support for CAPS exe

chrome/tools/crash_service/caps/main_win.cc

 // Copyright 2015 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 <windows.h>
 
+#include "base/at_exit.h"
+#include "base/files/file_path.h"
+#include "base/path_service.h"
+#include "base/version.h"
+#include "chrome/tools/crash_service/caps/logger_win.h"
+#include "chrome/tools/crash_service/caps/process_singleton_win.h"
+#include "chrome/tools/crash_service/caps/return_codes.h"
+
 int APIENTRY wWinMain(HINSTANCE instance, HINSTANCE prev, wchar_t*, int) {
-  return 0;
+  base::AtExitManager at_exit_manager;
+  base::FilePath dir_exe;
+  if (!PathService::Get(base::DIR_EXE, &dir_exe))
+    return caps::RC_INIT_ERROR;
+
+  // what directory we write depends if we are being run from the actual

[scottmg, 2015/02/01 19:55:35]

capital at start of comments

[cpu_(ooo_6.6-7.5), 2015/02/03 02:44:58]

Done.

+  // location (a versioned directory) or from a build output directory.
+  base::Version version(dir_exe.BaseName().MaybeAsASCII());
+  auto data_path = version.IsValid() ? dir_exe.DirName() : dir_exe;
+
+  // start logging.

[scottmg, 2015/02/01 19:55:35]

Do you want the logging start and the singleton check in this order? Will it be
able to open the same log for append in this order?

[cpu_(ooo_6.6-7.5), 2015/02/03 02:44:58]

Ya, it should be able to handle different processes with atomic writes, I will
test manually and at some point really test.

+  caps::Logger logger(data_path);
+
+  // check for an existing running instance.
+  caps::ProcessSingleton process_singleton;
+  if (process_singleton.other_instance())
+    return caps::RC_EXISTING_INSTANCE;
+
+  return caps::RC_NORMAL_EXIT;
 }
+