Made dart2js constructor lookup logic "private"-aware, fixed 4740 bug.

lib/compiler/implementation/ssa/builder.dart

Index: lib/compiler/implementation/ssa/builder.dart
diff --git a/lib/compiler/implementation/ssa/builder.dart b/lib/compiler/implementation/ssa/builder.dart
index d9995d5249d86d2a650a7b81f3f2dea15f9f8523..09952c0b844c52585802b83a80b6efeb398a35a0 100644
--- a/lib/compiler/implementation/ssa/builder.dart
+++ b/lib/compiler/implementation/ssa/builder.dart
@@ -1211,9 +1211,9 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
         assert(superClass !== null);
         assert(superClass.resolutionState == STATE_DONE);
         Selector selector =
-            new Selector.call(superClass.name, enclosingClass.getLibrary(), 0);
+            new Selector.callDefaultConstructor(enclosingClass.getLibrary());
         // TODO(johnniwinther): Should we find injected constructors as well?
-        FunctionElement target = superClass.lookupConstructor(superClass.name);
+        FunctionElement target = superClass.lookupConstructor(selector);
         if (target === null) {
           compiler.internalError("no default constructor available");
         }