Move frog/leg to lib/compiler/implementation.

lib/compiler/implementation/scanner/d8_scanner_bench.dart

 // Copyright (c) 2011, 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('d8_scanner_bench');
-#import('../../lib/node/node.dart');
+#import('../../node/node.dart');
 #import('scannerlib.dart');
 #import('scanner_implementation.dart');
 #import('scanner_bench.dart');
 
 d8_read(String filename) native 'return read(filename)';
 
 class D8ScannerBench extends ScannerBench {
   int getBytes(String filename, void callback(bytes)) {
     // This actually returns a buffer, not a String.
     var s = d8_read(filename);
     callback(s);
     return s.length;
   }
 
   Scanner makeScanner(bytes) => new StringScanner(bytes);
 
   void checkExistence(String filename) {
   }
 }
 
 main() {
   new D8ScannerBench().main(argv);
 }