Deferred (aka lazy) loading of static functions.

dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart

Index: dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart b/dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
index 8c43df5589a77a52f70df93cf77e2121ced29cc7..87cc5ef369388e25e2bfff233eb6d4b1d7e3c1df 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
@@ -5,6 +5,7 @@
 library elements.modelx;
 
 import 'dart:uri';
+import 'dart:collection' show LinkedHashMap;
 
 import 'elements.dart';
 import '../../compiler.dart' as api;
@@ -564,6 +565,9 @@ class LibraryElementX extends ElementX implements LibraryElement {
    */
   Link<Element> slotForExports;
 
+  final Map<LibraryDependency, LibraryElement> tagMapping =
+      new LinkedHashMap<LibraryDependency, LibraryElement>();
+
   LibraryElementX(Script script, [Uri canonicalUri, LibraryElement this.origin])
     : this.canonicalUri = ((canonicalUri == null) ? script.uri : canonicalUri),
       importScope = new Map<SourceString, Element>(),
@@ -590,6 +594,13 @@ class LibraryElementX extends ElementX implements LibraryElement {
     tags = tags.prepend(tag);
   }
 
+  void resolvedTag(LibraryDependency tag, LibraryElement library) {
+    assert(tagMapping[tag] == null);
+    tagMapping[tag] = library;
+  }
+
+  LibraryElement getDependency(LibraryDependency tag) => tagMapping[tag];
+
   /**
    * Adds [element] to the import scope of this library.
    *