Add link to BMU benchmark gallery generator tool.

runtime/tools/verbose_gc_to_bmu.dart

 // Copyright (c) 2014, 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.
-
+//
+// NOTE: See also wrapper script sdk/runtime/tools/bmu_benchmark_gallery.sh
+//
 // Tool to compute bounded mutator utilization (BMU) from a --verbose_gc log.
 // Outputs CSV suitable for, e.g., gnuplot:
 //
 // dart --verbose_gc foo.dart 2> foo.gclog
 // dart verbose_gc_to_bmu.dart < foo.gclog > foo.bmu
 // gnuplot -p -e "set yr [0:1]; set logscale x; plot 'foo.bmu' with linespoints"
 
 import 'dart:io';
 import 'dart:math';
 
@@ skipping 81 matching lines @@
   }
   print('# window_size_ms, bounded_mutator_utilization');
   var minimumSeen = 1.0;
   for (int w = t._run.length;
        w > 1000 * MINIMUM_WINDOW_SIZE_MS;
        w = (w * WINDOW_STEP_FACTOR).floor()) {
     minimumSeen = min(minimumSeen, t.minUtilization(w));
     print('${w / 1000}, $minimumSeen');
   }
 }