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
+
+// firstrunCheckNotInstalled is a sanity check to make sure that the user really
+// wants to do firstrun again, if it looks like cr is already installed.
+func firstrunCheckNotInstalled() {
+        // Check to see if a path ending in 'cr/bin' in in %PATH%.
+        // Check to see if an executable called 'cr.exe' is in that path.
+}
+
+// firstrunPromptInstallDir prompts the user for a directory path to install.
+func firstrunPromptInstallDir() {
+        // Figure out a sane place to suggest.
+        // Suggest it and ask the user for an alternative.
+        // Check that the chosen directory makes sense.
+}
+
+// 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() {
+
+}
+
+// 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() {
+
+}
+
+// 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() {
+
+}