Add a hashCode to Command so reporting timings is 400 faster.

dart/tools/testing/dart/test_runner.dart

Index: dart/tools/testing/dart/test_runner.dart
diff --git a/dart/tools/testing/dart/test_runner.dart b/dart/tools/testing/dart/test_runner.dart
index 3ccc3eedab0547c5c78251519380f15fa38a5035..1298982eb53391ad23a7ee965ce9b042095816cf 100644
--- a/dart/tools/testing/dart/test_runner.dart
+++ b/dart/tools/testing/dart/test_runner.dart
@@ -76,6 +76,10 @@ int findBytes(List<int> data, List<int> pattern, [int startPos=0]) {
 
 /** A command executed as a step in a test case. */
 class Command {
+  static int nextHashCode = 0;
+  final int hashCode = nextHashCode++;
+  operator ==(other) => super == (other);
+
   /** Path to the executable of this command. */
   String executable;