dart2js cps: More aggressive operator specialization.

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

Index: pkg/compiler/lib/src/js_backend/codegen/codegen.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/codegen.dart b/pkg/compiler/lib/src/js_backend/codegen/codegen.dart
index 1815ee2a8b7905d76029859c51408e619a36cdf8..eb1e6994d4ea067c3c39c1f53e7eb9232c212d64 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/codegen.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/codegen.dart
@@ -1031,7 +1031,7 @@ class CodeGenerator extends tree_ir.StatementVisitor
   }
 
   @override
-  visitNullCheck(tree_ir.NullCheck node) {
+  visitReceiverCheck(tree_ir.ReceiverCheck node) {
     js.Expression value = visitExpression(node.value);
     // TODO(sra): Try to use the selector even when [useSelector] is false. The
     // reason we use 'toString' is that it is always defined so avoids a slow
@@ -1041,9 +1041,12 @@ class CodeGenerator extends tree_ir.StatementVisitor
     // hook for that selector. We don't know these things here, but the decision
     // could be deferred by creating a deferred property that was resolved after
     // codegen.
-    js.Expression access = node.selector != null && node.useSelector
+    js.Expression access = node.useSelector
         ? js.js('#.#', [value, glue.invocationName(node.selector)])
         : js.js('#.toString', [value]);
+    if (node.useInvoke) {
+      access = new js.Call(access, []);
+    }
     if (node.condition != null) {
       js.Expression condition = visitExpression(node.condition);
       js.Statement body = isNullReturn(node.next)