pkg/compiler: fix imports

pkg/compiler/lib/src/hash/sha1.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * SHA-1.
  * Ripped from package:crypto.
  */
 library sha1;
 
+import 'dart:convert';
 import 'dart:math' show pow;
-import 'dart:convert';
 
 import '../io/code_output.dart' show CodeOutputListener;
 
 class Hasher implements CodeOutputListener {
   Hash _hasher = new SHA1();
   String _hashString;
 
   @override
   void onDone(int length) {
     // Do nothing.
@@ skipping 338 matching lines @@
       int y = bytes[i + 1];
       out[j++] = lookup.codeUnitAt(x >> 2);
       out[j++] = lookup.codeUnitAt(((x << 4) | (y >> 4)) & 0x3F);
       out[j++] = lookup.codeUnitAt((y << 2) & 0x3F);
       out[j++] = PAD;
     }
 
     return new String.fromCharCodes(out);
   }
 }