Extract DiagnosticReporter implementation from Compiler.

pkg/compiler/lib/src/scanner/scanner_task.dart

 // Copyright (c) 2012, 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 dart2js.scanner.task;
 
 import '../common/tasks.dart' show
     CompilerTask;
 import '../compiler.dart' show
     Compiler;
@@ skipping 12 matching lines @@
 
 class ScannerTask extends CompilerTask {
   ScannerTask(Compiler compiler) : super(compiler);
   String get name => 'Scanner';
 
   void scanLibrary(LibraryElement library) {
     CompilationUnitElement compilationUnit = library.entryCompilationUnit;
     String canonicalUri = library.canonicalUri.toString();
     String resolvedUri = compilationUnit.script.resourceUri.toString();
     if (canonicalUri == resolvedUri) {
-      compiler.log("Scanning library $canonicalUri");
+      reporter.log("Scanning library $canonicalUri");
     } else {
-      compiler.log("Scanning library $canonicalUri ($resolvedUri)");
+      reporter.log("Scanning library $canonicalUri ($resolvedUri)");
     }
     scan(compilationUnit);
   }
 
   void scan(CompilationUnitElement compilationUnit) {
     measure(() {
       scanElements(compilationUnit);
     });
   }
 
@@ skipping 14 matching lines @@
    * value ('\x00'). If [source] does not end with '0', the string is copied
    * before scanning.
    */
   Token tokenize(String source) {
     return measure(() {
       return new StringScanner.fromString(source, includeComments: false)
           .tokenize();
     });
   }
 }