Rename StopWatch to Stopwatch. Add new Stopwatch.start() and Stopwatch.reset().

frog/leg/scanner/scanner_bench.dart

Index: frog/leg/scanner/scanner_bench.dart
diff --git a/frog/leg/scanner/scanner_bench.dart b/frog/leg/scanner/scanner_bench.dart
index 7e2513428b8b740320e8e4e9a7b89b4acd75ee73..ea047fb8f91de6533de360e32e72e3b5bacf729e 100644
--- a/frog/leg/scanner/scanner_bench.dart
+++ b/frog/leg/scanner/scanner_bench.dart
@@ -25,7 +25,7 @@ class ScannerBench {
     bar.begin();
     for (int i = 0; i < iterations; i++) {
       bar.tick();
-      StopWatch timer = new StopWatch();
+      Stopwatch timer = new Stopwatch();
       timer.start();
       int charCount = 0;
       for (final String argument in arguments) {