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

lib/compiler/implementation/compile_time_constants.dart

Index: lib/compiler/implementation/compile_time_constants.dart
diff --git a/lib/compiler/implementation/compile_time_constants.dart b/lib/compiler/implementation/compile_time_constants.dart
index ac998f9c34c23ff24de6a0bf8664ef5380a77a67..7c9bc475b460de074065095d0ecaee2da516e5dd 100644
--- a/lib/compiler/implementation/compile_time_constants.dart
+++ b/lib/compiler/implementation/compile_time_constants.dart
@@ -753,7 +753,8 @@ class ConstructorEvaluator extends CompileTimeConstantEvaluator {
         assert(superClass !== null);
         assert(superClass.resolutionState == STATE_DONE);
         FunctionElement targetConstructor =
-            superClass.lookupConstructor(superClass.name);
+            superClass.lookupConstructor(enclosingClass.getLibrary(),

[kasperl, 2012/09/19 05:59:17]

Could we start using the selector to lookup the constructor instead? We compute
the selector below and it contains all the information we need.

+                                         superClass.name);
         if (targetConstructor === null) {
           compiler.internalError("no default constructor available",
                                  node: functionNode);