Load patches via callback.

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

Index: sdk/lib/_internal/compiler/implementation/elements/modelx.dart
diff --git a/sdk/lib/_internal/compiler/implementation/elements/modelx.dart b/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
index 629678b49dfd74006c17740db9112073082b9fd3..64bcdcfd21dd3bce7dccdc8fd39b62d142d916c8 100644
--- a/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
+++ b/sdk/lib/_internal/compiler/implementation/elements/modelx.dart
@@ -970,11 +970,11 @@ class LibraryElementX
 
   String toString() {
     if (origin != null) {
-      return 'patch library(${getLibraryOrScriptName()})';
+      return 'patch library(${canonicalUri})';
     } else if (patch != null) {
-      return 'origin library(${getLibraryOrScriptName()})';
+      return 'origin library(${canonicalUri})';
     } else {
-      return 'library(${getLibraryOrScriptName()})';
+      return 'library(${canonicalUri})';
     }
   }