Prepare for development branch by updating externally-used API.

pkg/front_end/lib/src/fasta/loader.dart

Index: pkg/front_end/lib/src/fasta/loader.dart
diff --git a/pkg/front_end/lib/src/fasta/loader.dart b/pkg/front_end/lib/src/fasta/loader.dart
index 6f4bbb730890e45ff9d2a58aa1601802e9d056e6..2b20bd08341ef381e7117ecdd68a2b88dcce67a4 100644
--- a/pkg/front_end/lib/src/fasta/loader.dart
+++ b/pkg/front_end/lib/src/fasta/loader.dart
@@ -43,7 +43,8 @@ abstract class Loader<L> {
   ///
   /// Canonical URIs have schemes like "dart", or "package", and the actual
   /// location is often a file URI.
-  LibraryBuilder read(Uri uri, [Uri fileUri]) {
+  LibraryBuilder read(Uri uri, int charOffset,
+      {Uri fileUri, LibraryBuilder accessor}) {

[ahe, 2017/05/23 15:04:24]

The accessor will be used to ensure that private dart libraries, such as
dart:_builtin can't be imported by user code.

[scheglov, 2017/05/23 16:14:45]

Please document new parameters.

[ahe, 2017/05/24 10:54:20]

Done.

     firstSourceUri ??= uri;
     LibraryBuilder builder = builders.putIfAbsent(uri, () {
       if (fileUri == null) {
@@ -74,7 +75,7 @@ abstract class Loader<L> {
 
   void ensureCoreLibrary() {
     if (coreLibrary == null) {
-      read(Uri.parse("dart:core"));
+      read(Uri.parse("dart:core"), -1);
       assert(coreLibrary != null);
     }
   }