dart2js cps: Support --trust-primitives and --trust-type-annotations.

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

Index: pkg/compiler/lib/src/cps_ir/remove_refinements.dart
diff --git a/pkg/compiler/lib/src/cps_ir/remove_refinements.dart b/pkg/compiler/lib/src/cps_ir/remove_refinements.dart
index 98f1c17a8867dd072bc56f7d1d30d89566f965a7..2d49c95602fa8a15541c90790d9de0ad6f4675a3 100644
--- a/pkg/compiler/lib/src/cps_ir/remove_refinements.dart
+++ b/pkg/compiler/lib/src/cps_ir/remove_refinements.dart
@@ -23,7 +23,11 @@ class RemoveRefinements extends TrampolineRecursiveVisitor implements Pass {
     Expression next = node.body;
     if (node.primitive is Refinement) {
       Refinement refinement = node.primitive;
-      refinement.value.definition.substituteFor(refinement);
+      Primitive value = refinement.value.definition;
+      if (refinement.hint != null && value.hint == null) {
+        value.hint = refinement.hint;
+      }
+      value.substituteFor(refinement);
       refinement.destroy();
       node.remove();
     }