Remove package imports from itself.

pkg/front_end/lib/src/fasta/source/source_loader.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library fasta.source_loader;
 
 import 'dart:async' show Future;
 
 import 'dart:io' show FileSystemException;
 
-import 'package:front_end/src/fasta/scanner/io.dart' show readBytesFromFile;
+import '../scanner/io.dart' show readBytesFromFile;
 
-import 'package:front_end/src/fasta/scanner.dart'
-    show ErrorToken, ScannerResult, Token, scan;
+import '../scanner.dart' show ErrorToken, ScannerResult, Token, scan;
 
-import 'package:front_end/src/fasta/parser/class_member_parser.dart'
-    show ClassMemberParser;
+import '../parser/class_member_parser.dart' show ClassMemberParser;
 
 import 'package:kernel/ast.dart' show Program;
 
 import 'package:kernel/class_hierarchy.dart' show ClassHierarchy;
 
 import 'package:kernel/core_types.dart' show CoreTypes;
 
 import '../errors.dart' show inputError, printUnexpected;
 
 import '../messages.dart' show warning;
@@ skipping 318 matching lines @@
     ticker.logMs("Built analyzer element model.");
   }
 
   void computeHierarchy(Program program) {
     hierarchy = new ClassHierarchy(program);
     ticker.logMs("Computed class hierarchy");
     coreTypes = new CoreTypes(program);
     ticker.logMs("Computed core types");
   }
 }