Introduce mkgrokdump to update tools/v8heapconst.py.

test/mkgrokdump/mkgrokdump.gyp

+# 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.
+
+{
+  'variables': {
+    'v8_code': 1,
+  },
+  'includes': ['../../gypfiles/toolchain.gypi', '../../gypfiles/features.gypi'],
+  'targets': [
+    {
+      'target_name': 'mkgrokdump',
+      'type': 'executable',
+      'dependencies': [
+        '../../src/v8.gyp:v8',
+        '../../src/v8.gyp:v8_libbase',
+        '../../src/v8.gyp:v8_libplatform',
+      ],
+      'include_dirs': [
+        '../..',
+      ],
+      'sources': [
+        'mkgrokdump.cc',
+      ],
+    },
+  ],
+  'conditions': [
+    ['test_isolation_mode != "noop"', {
+      'targets': [
+        {
+          'target_name': 'mkgrokdump_run',
+          'type': 'none',
+          'dependencies': [
+            'mkgrokdump',
+          ],
+          'includes': [
+            '../../gypfiles/isolate.gypi',
+          ],
+          'sources': [
+            'mkgrokdump.isolate',
+          ],
+        },
+      ],
+    }],
+  ],
+}