Make source information on conditions mandatory in CPS

pkg/compiler/lib/src/cps_ir/cps_fragment.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 cps_ir.cps_fragment;
 
 import 'cps_ir_nodes.dart';
 import '../constants/values.dart';
 import '../universe/selector.dart' show Selector;
 import '../types/types.dart' show TypeMask;
@@ skipping 182 matching lines @@
   /// Returns a new fragment for the 'then' branch, or the 'else' branch
   /// if [negate] is true.
   ///
   /// The other branch becomes the new hole.
   CpsFragment branch(Primitive condition,
                      {bool negate: false,
                       bool strict: false}) {
     Continuation trueCont = new Continuation(<Parameter>[]);
     Continuation falseCont = new Continuation(<Parameter>[]);
     put(new LetCont.two(trueCont, falseCont,
-            new Branch(condition, trueCont, falseCont, strict: strict)));
+            new Branch(condition, trueCont, falseCont,
+                       sourceInformation, strict: strict)));
     if (negate) {
       context = trueCont;
       return new CpsFragment(sourceInformation, falseCont);
     } else {
       context = falseCont;
       return new CpsFragment(sourceInformation, trueCont);
     }
   }
 
   /// Branch on [condition].
@@ skipping 156 matching lines @@
   while (prim.firstRef != null) {
     Refinement refine = prim.firstRef.parent;
     destroyRefinementsOfDeadPrimitive(refine);
     LetPrim letPrim = refine.parent;
     InteriorNode parent = letPrim.parent;
     parent.body = letPrim.body;
     letPrim.body.parent = parent;
     prim.firstRef.unlink();
   }
 }