Remove deprecated api from LibraryBuilder.

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 c2a791aa71392c324de66538772b38a3ba290e59..08fa08f19c91f5496456f486eb91d12af4418d5a 100644
--- a/pkg/front_end/lib/src/fasta/loader.dart
+++ b/pkg/front_end/lib/src/fasta/loader.dart
@@ -13,7 +13,8 @@ import 'builder/builder.dart' show Builder, LibraryBuilder;
 import 'deprecated_problems.dart'
     show firstSourceUri, deprecated_printUnexpected;
 
-import 'messages.dart' show LocatedMessage, Message, templateUnspecified;
+import 'messages.dart'
+    show LocatedMessage, Message, messagePlatformPrivateLibraryAccess;
 
 import 'target_implementation.dart' show TargetImplementation;
 
@@ -103,8 +104,8 @@ abstract class Loader<L> {
         uri.scheme == "dart" &&
         uri.path.startsWith("_") &&
         accessor.uri.scheme != "dart") {
-      accessor.deprecated_addCompileTimeError(
-          charOffset, "Can't access platform private library.");
+      accessor.addCompileTimeError(
+          messagePlatformPrivateLibraryAccess, charOffset, accessor.fileUri);
     }
     return builder;
   }
@@ -179,17 +180,6 @@ ${format(ms / libraryCount, 3, 12)} ms/compilation unit.""");
         .add(message.withLocation(fileUri, charOffset));
   }
 
-  void deprecated_addCompileTimeError(
-      Uri fileUri, int charOffset, String message,
-      {bool silent: false, bool wasHandled: false}) {
-    if (!silent) {
-      deprecated_printUnexpected(fileUri, charOffset, message);
-    }
-    (wasHandled ? handledErrors : unhandledErrors).add(templateUnspecified
-        .withArguments(message)
-        .withLocation(fileUri, charOffset));
-  }
-
   Builder getAbstractClassInstantiationError() {
     return target.getAbstractClassInstantiationError(this);
   }