Add beginnings of new cr command

go/src/infra/tools/cr/cmd/firstrun/firstrun_windows.go

+// 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.
+
+// Windows-specific function implementations for the firstrun subcommand.
+
+package firstrun
+
+import (
+        "errors"
+)
+
+var executableName = "cr.exe"
+
+// firstrunPromptInstallDir prompts the user for a directory path to install.
+func firstrunPromptInstallDir() (string, error) {
+        return "", errors.New("firstrun_windows.firstrunPromptInstallDir not yet implemented")
+}
+
+// firstrunInitInstallDir sets up the selected directory to house cr. It creates
+// the modules/ and bin/ subdirectories, places cr.exe in the top level, and
+// symlinks it into bin/.
+func firstrunInitInstallDir(dir string) error {
+        return errors.New("firstrun_windows.firstrunInitInstallDir not yet implemented")
+}
+
+// firstrunUpdatePath finds the registry entry for %PATH%, sees if it can
+// automatically update it, and prompts the user for permission to do so.
+func firstrunUpdatePath(dir string) error {
+        return errors.New("firstrun_windows.firstrunUpdatePath not yet implemented")
+}
+
+// firstrunPrintUpdatePathInstructions prints instructions for the user to
+// update their %PATH% manually. This is used if updatePath fails, or if the
+// user declines to have their registry updated automatically.
+func firstrunPrintUpdatePathInstructions() error {
+        return errors.New("firstrun_windows.firstrunPrintUpdatePathInstructions not yet implemented")
+}