pkg/compiler: fix imports

pkg/compiler/lib/src/cps_ir/loop_hierarchy.dart

 // Copyright (c) 2015, 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.
 
 library dart2js.cps_ir.loop_hierarchy;
 
+import 'cps_fragment.dart';
 import 'cps_ir_nodes.dart';
-import 'cps_fragment.dart';
 
 /// Determines the effective nesting of loops.
 ///
 /// The effective nesting of loops is different from the lexical nesting, since
 /// recursive continuations can generally contain all the code following
 /// after the loop in addition to the looping code itself.
 ///
 /// For example, the 'else' branch below is not effectively part of the loop:
 ///
 ///   let rec kont x =
@@ skipping 147 matching lines @@
   /// surrounding the inserted fragment.
   void update(CpsFragment fragment,
       {Continuation exitLoop, Continuation catchLoop}) {
     if (fragment.isEmpty) return;
     _exitLoop = exitLoop;
     _currentDepth = getDepth(exitLoop);
     _processBlock(fragment.root, catchLoop);
     _exitLoop = null;
   }
 }