dart2js cps: Add path-sensitive types by inserting refinement IR nodes.

pkg/compiler/lib/src/js_backend/codegen/task.dart

Index: pkg/compiler/lib/src/js_backend/codegen/task.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/task.dart b/pkg/compiler/lib/src/js_backend/codegen/task.dart
index 16c882ac3274d7786dbf57624bdc633ae3dfdaee..654f5052401971337461c14b99c23c604fecd076 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/task.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/task.dart
@@ -170,9 +170,11 @@ class CpsFunctionCompiler implements FunctionCompiler {
       assert(checkCpsIntegrity(cpsNode));
     }
 
+    applyCpsPass(new InsertRefinements(compiler.typesTask, compiler.world));
     TypePropagator typePropagator = new TypePropagator(compiler, this);
     applyCpsPass(typePropagator);
     dumpTypedIR(cpsNode, typePropagator);
+    applyCpsPass(new RemoveRefinements());
     applyCpsPass(new LoopInvariantCodeMotion());
     applyCpsPass(new ShareInterceptors());
     applyCpsPass(new ScalarReplacer(compiler));