dart2js cps: Fix a comment.

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

 library dart2js.cps_ir.loop_invariant_branch;
 
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart';
 import 'loop_hierarchy.dart';
 import 'cps_fragment.dart';
 import 'redundant_join.dart' show AlphaRenamer;
 
 /// Hoists branches out of loops, where:
 /// - the branch is at the entry point of a loop
@@ skipping 77 matching lines @@
     while (exp is LetCont) {
       exp = exp.next;
     }
     return exp;
   }
 
   /// Adds [parameters] to [cont] and updates every invocation to pass the
   /// corresponding parameter values as arguments. Thus, the parameters are
   /// passed in explicitly instead of being captured.
   ///
-  /// This only works because [AlphaRenamer] cleans up after this pass.
+  /// This only works because [AlphaRenamer] cleans up at the end of this pass.
   ///
   /// Schematically:
   ///
   ///     let outer(x1, x2, x3) =
   ///       let inner(y) = BODY
   ///       [ .. inner(y') .. ]
   ///
   ///   ==> (append parameters)
   ///
   ///     let outer(x1, x2, x3) =
@@ skipping 134 matching lines @@
     //   in loop(i)
     //
     destroyAndReplace(branch, new InvokeContinuation(loopCase, []));
 
     // Record that at least one branch was hoisted to trigger alpha renaming.
     wasHoisted = true;
 
     return true;
   }
 }