Fixed sdk/bin/dart2js.bat to enable SDK_DIRs with spaces in them

sdk/bin/dart2js.bat

Index: sdk/bin/dart2js.bat
diff --git a/sdk/bin/dart2js.bat b/sdk/bin/dart2js.bat
index e8f44e22e1d4890972d20fec384ddd06557b9f9f..be0219f4cc4ad5c6d1f7520aa1bdb808ae016c59 100644
--- a/sdk/bin/dart2js.bat
+++ b/sdk/bin/dart2js.bat
@@ -14,7 +14,10 @@ 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
 
-set DART2JS=%SDK_DIR%lib\_internal\compiler\implementation\dart2js.dart
+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\utils_wrapper.dart.snapshot
 
@@ -27,7 +30,7 @@ if _%DART2JS_DEVELOPER_MODE%_ == _1_ (
 
 if exist "%SNAPSHOT%" (
   echo Using snapshot "%SNAPSHOT%" >&2
-  set EXTRA_OPTIONS=%EXTRA_OPTIONS% --library-root=%SDK_DIR%
+  set EXTRA_OPTIONS=%EXTRA_OPTIONS% "--library-root=%SDK_DIR%"
 )
 
 rem See comments regarding options below in dart2js shell script.