dart2js cps_ir: Use interceptors for is-checks.

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

Index: pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
index ca34d15f0107b02e2801c7f76694381a6ef593f1..480086b7b10b057602f0dfb83cc506d18394755b 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart
@@ -2753,7 +2753,11 @@ class IrBuilder {
         // `x is Null` is true if and only if x is null.
         return _buildCheckNull(value);
       }
-      return addPrimitive(new ir.TypeTest(value, type, typeArguments));
+      if (type.isInterfaceType && type.isRaw) {

[sra1, 2015/10/06 06:47:58]

I think this could me moved to type_propagation.

[sra1, 2015/10/07 04:01:06]

Done.

+        return addPrimitive(new ir.TypeTestRaw(value, type));
+      } else {
+        return addPrimitive(new ir.TypeTest(value, type, typeArguments));
+      }
     } else {
       if (type.isObject || type.isDynamic) {
         // `x as Object` and `x as dynamic` are the same as `x`.