Revert "Move dart2js from sdk/lib/_internal/compiler to pkg/compiler"

sdk/bin/dart2js.bat

 @echo off
 REM Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 REM for details. All rights reserved. Use of this source code is governed by a
 REM BSD-style license that can be found in the LICENSE file.
 
 setlocal
 rem Handle the case where dart-sdk/bin has been symlinked to.
 set DIR_NAME_WITH_SLASH=%~dp0
 set DIR_NAME=%DIR_NAME_WITH_SLASH:~0,-1%%
 call :follow_links "%DIR_NAME%", RETURNED_BIN_DIR
 rem Get rid of surrounding quotes.
 for %%i in ("%RETURNED_BIN_DIR%") do set BIN_DIR=%%~fi
 
 rem Get absolute full name for SDK_DIR.
 for %%i in ("%BIN_DIR%\..\") do set SDK_DIR=%%~fi
 
 rem Remove trailing backslash if there is one
 IF %SDK_DIR:~-1%==\ set SDK_DIR=%SDK_DIR:~0,-1%
 
+set DART2JS=%SDK_DIR%\lib\_internal\compiler\implementation\dart2js.dart
 set DART=%BIN_DIR%\dart
+set SNAPSHOT=%BIN_DIR%\snapshots\dart2js.dart.snapshot
 
 set EXTRA_OPTIONS=
 set EXTRA_VM_OPTIONS=
 
 if _%DART2JS_DEVELOPER_MODE%_ == _1_ (
   set EXTRA_VM_OPTIONS=%EXTRA_VM_OPTIONS% --checked
 )
 
+if exist "%SNAPSHOT%" (
+  set EXTRA_OPTIONS=%EXTRA_OPTIONS% "--library-root=%SDK_DIR%"
+)
+
 rem See comments regarding options below in dart2js shell script.
 set EXTRA_VM_OPTIONS=%EXTRA_VM_OPTIONS% --heap_growth_rate=512
 
 rem We allow extra vm options to be passed in through an environment variable.
 if not "_%DART_VM_OPTIONS%_" == "__" (
   set EXTRA_VM_OPTIONS=%EXTRA_VM_OPTIONS% %DART_VM_OPTIONS%
 )
 
-rem Get absolute full name for DART_ROOT.
-for %%i in ("%SDK_DIR%\..\") do set DART_ROOT=%%~fi
-
-rem Remove trailing backslash if there is one
-if %DART_ROOT:~-1%==\ set DART_ROOT=%DART_ROOT:~0,-1%
-
-set DART2JS=%DART_ROOT%\pkg\compiler\lib\src\dart2js.dart
-
-rem DART_CONFIGURATION defaults to ReleaseIA32
-if "%DART_CONFIGURATION%"=="" set DART_CONFIGURATION=ReleaseIA32
-
-set BUILD_DIR=%DART_ROOT%\build\%DART_CONFIGURATION%
-
-set PACKAGE_ROOT=%BUILD_DIR%\packages
-
-"%DART%" %EXTRA_VM_OPTIONS% "--package-root=%PACKAGE_ROOT%" "%DART2JS%" %EXTRA_OPTIONS% %*
+if exist "%SNAPSHOT%" (
+  "%DART%" %EXTRA_VM_OPTIONS% "%SNAPSHOT%" %EXTRA_OPTIONS% %*
+) else (
+  "%DART%" %EXTRA_VM_OPTIONS% "%DART2JS%" %EXTRA_OPTIONS% %*
+)
 
 endlocal
 
 exit /b %errorlevel%
 
 :follow_links
 setlocal
 for %%i in (%1) do set result=%%~fi
 set current=
 for /f "usebackq tokens=2 delims=[]" %%i in (`dir /a:l "%~dp1" 2^>nul ^
                                              ^| find ">     %~n1 ["`) do (
   set current=%%i
 )
 if not "%current%"=="" call :follow_links "%current%", result
 endlocal & set %~2=%result%
 goto :eof
 
 :end