Adding windows batch file to complement the bash script.

bin/flutter.bat

+@ECHO off
+REM Copyright 2015 The Chromium Authors. All rights reserved.
+REM Use of this source code is governed by a BSD-style license that can be
+REM found in the LICENSE file.
+
+SETLOCAL ENABLEDELAYEDEXPANSION
+FOR %%i IN ("%~dp0..") DO SET "flutter_root=%%~fi" REM Get the parent directory
+SET flutter_tools_dir=%flutter_root%\packages\flutter_tools
+SET snapshot_path=%flutter_root%\bin\cache\flutter_tools.snapshot
+SET stamp_path=%flutter_root%\bin\cache\flutter_tools.stamp
+SET script_path=%flutter_tools_dir%\bin\sky_tools.dart
+REM TODO: Don't require dart to be on the user's path
+SET dart=dart
+
+REM Getting modified timestamps in a batch file is ... troublesome
+REM More info: http://stackoverflow.com/questions/1687014/how-do-i-compare-timestamps-of-files-in-a-dos-batch-script
+FOR %%f IN (%flutter_tools_dir%\pubspec.yaml) DO SET yamlt=%%~tf
+FOR %%a IN (%flutter_tools_dir%\pubspec.lock) DO SET lockt=%%~ta
+if !lockt! LSS !yamlt! (
+    CD "%flutter_tools_dir%"
+    CALL pub.bat get
+    CD "%flutter_root%"
+    IF EXIST %snapshot_path% DEL %snapshot_path%
+)
+
+REM IF doesn't have an "or". Instead, just use GOTO
+FOR /f %%r IN ('git rev-parse HEAD') DO SET revision=%%r
+IF NOT EXIST %snapshot_path% GOTO do_snapshot
+IF NOT EXIST %stamp_path% GOTO do_snapshot
+FOR /f %%r IN ('type "%stamp_path%"') DO SET stamp_value=%%r
+IF (!stamp_value! NEQ !revision!) GOTO do_snapshot
+
+GOTO :after_snapshot
+
+:do_snapshot
+
+CALL %dart% --snapshot="%snapshot_path%" --package-root="%flutter_tools_dir%\packages" "%script_path%"
+ECHO !revision! > "%stamp_path%"
+
+:after_snapshot
+
+CALL %dart% "%snapshot_path%" %*
+
+IF /I "%ERRORLEVEL%" EQU "253" (
+   CALL %dart% --snapshot="%snapshot_path%" --package-root="%flutter_tools_dir%\packages" "%script_path%"
+   CALL %dart% "%snapshot_path%" %*
+)
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