pkg/compiler: fix imports

pkg/compiler/lib/src/tree_ir/optimization/logical_rewriter.dart

 // Copyright (c) 2014, 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 tree_ir.optimization.logical_rewriter;
 
+import '../../constants/values.dart' as values;
 import '../tree_ir_nodes.dart';
 import 'optimization.dart' show Pass;
-import '../../constants/values.dart' as values;
 
 /// Rewrites logical expressions to be more compact in the Tree IR.
 ///
 /// In this class an expression is said to occur in "boolean context" if
 /// its result is immediately applied to boolean conversion.
 ///
 /// IF STATEMENTS:
 ///
 /// We apply the following two rules to [If] statements (see [visitIf]).
 ///
@@ skipping 537 matching lines @@
     } else if (e1 is Assign) {
       return e2 is VariableUse && e1.variable == e2.variable;
     }
     return false;
   }
 
   void destroyVariableUse(VariableUse node) {
     --node.variable.readCount;
   }
 }