Introduce mkgrokdump to update tools/v8heapconst.py.

test/v8heapconst/v8heapconst.status

Index: test/v8heapconst/v8heapconst.status
diff --git a/test/v8heapconst/v8heapconst.status b/test/v8heapconst/v8heapconst.status
new file mode 100644
index 0000000000000000000000000000000000000000..9e7a02777b9251295125f723906838950ddaea90
--- /dev/null
+++ b/test/v8heapconst/v8heapconst.status
@@ -0,0 +1,13 @@
+# Copyright 2017 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+[
+# Only test for default mode x64.
+['variant != default', {

[Michael Achenbach, 2017/04/11 09:45:54]

nit: You could write it in one line:
variant != default or arch != x64

[Yang, 2017/04/11 09:57:20]

Done.

+  '*': [SKIP],
+}],  # variant != default
+['arch != x64', {
+  '*': [SKIP],
+}],  # variant != default
+]