Internal libraries supported.

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

Index: sdk/lib/_internal/compiler/implementation/elements/elements.dart
diff --git a/sdk/lib/_internal/compiler/implementation/elements/elements.dart b/sdk/lib/_internal/compiler/implementation/elements/elements.dart
index 0ac36d2172090b9b481ffd947ed47beb9a806272..8d94a9d39dbf9f91da055432e25646126bd671c5 100644
--- a/sdk/lib/_internal/compiler/implementation/elements/elements.dart
+++ b/sdk/lib/_internal/compiler/implementation/elements/elements.dart
@@ -470,14 +470,30 @@ abstract class CompilationUnitElement extends Element {
 }
 
 abstract class LibraryElement extends Element implements ScopeContainerElement {
-  Uri get uri;
+  /**
+   * The canonical uri for this library.
+   *
+   * For user libraries the canonical uri is the script uri. For platform
+   * libraries the canonical uri is of the form [:dart:x:].
+   */
+  Uri get canonicalUri;
   CompilationUnitElement get entryCompilationUnit;
   Link<CompilationUnitElement> get compilationUnits;
   Link<LibraryTag> get tags;
   LibraryName get libraryTag;
   Link<Element> get exports;
 
+  /**
+   * [:true:] if this library is part of the platform, that is its canonical
+   * uri has the scheme 'dart'.
+   */
   bool get isPlatformLibrary;
+
+  /**
+   * [:true:] if this library is a platform library whose path starts with
+   * an underscore.
+   */
+  bool get isInternalLibrary;
   bool get canUseNative;
   bool get exportsHandled;