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

lib/compiler/implementation/universe/universe.dart

Index: lib/compiler/implementation/universe/universe.dart
diff --git a/lib/compiler/implementation/universe/universe.dart b/lib/compiler/implementation/universe/universe.dart
index 645d71b77b5173cfe4910803a83634a1f1891eda..3ba33605c1bfbba86c86c01cd5790d0de925629d 100644
--- a/lib/compiler/implementation/universe/universe.dart
+++ b/lib/compiler/implementation/universe/universe.dart
@@ -123,6 +123,7 @@ class Selector implements Hashable {
   final SelectorKind kind;
   final SourceString name;
   final LibraryElement library; // Library is null for non-private selectors.
+  final SourceString normalizedConstructorName;
 
   // The numbers of arguments of the selector. Includes named arguments.
   final int argumentCount;
@@ -134,13 +135,15 @@ class Selector implements Hashable {
       SourceString name,
       LibraryElement library,
       this.argumentCount,
-      [List<SourceString> namedArguments = const <SourceString>[]])
+      [List<SourceString> namedArguments = const <SourceString>[],
+      SourceString normalizedConstructorName = null])
     : this.name = name,
       this.library = name.isPrivate() ? library : null,
       this.namedArguments = namedArguments,
       this.orderedNamedArguments = namedArguments.isEmpty()
           ? namedArguments
-          : <SourceString>[] {
+          : <SourceString>[],
+      this.normalizedConstructorName = normalizedConstructorName {
     assert(!name.isPrivate() || library != null);
   }
 
@@ -187,6 +190,20 @@ class Selector implements Hashable {
       : this(SelectorKind.CALL, Compiler.CALL_OPERATOR_NAME, null,
              selector.argumentCount, selector.namedArguments);
 
+  Selector.callConstructor(SourceString className,
+                           SourceString constructorName,
+                           LibraryElement library)
+      : this(SelectorKind.CALL,
+             constructorName,
+             library,
+             0,
+             const [],
+             Elements.constructConstructorName(className, constructorName));
+
+  Selector.callDefaultConstructor(SourceString name,
+                                  LibraryElement library)
+      : this(SelectorKind.CALL, name, library, 0, const [], name);
+
   // TODO(kasperl): This belongs somewhere else.
   Selector.noSuchMethod()
       : this(SelectorKind.CALL, Compiler.NO_SUCH_METHOD, null, 2);