Land D8 6.1.0 again, avoid using D8 Worker

third_party/d8/README.google

Index: third_party/d8/README.google
diff --git a/third_party/d8/README.google b/third_party/d8/README.google
index f5e801cf5c26d4ff2d999d12257c2ded86fae4d3..2f3b067e08100bc07493b1d75a12e086f133bce3 100644
--- a/third_party/d8/README.google
+++ b/third_party/d8/README.google
@@ -1,14 +1,18 @@
 Name: V8 command line javascript shell.
 Short Name: d8
-URL: https://chromium.googlesource.com/v8/v8/+/4.4.63.5
-Version: 4.4.63.5
-Revision: 288da5c7788134004a4b34a4ba0cb4814428cf7c
-Date: September 2nd 2014
+URL: https://chromium.googlesource.com/v8/v8/+/efdf8385488430cb3fc15a37ca284c4e2ea1b97f
+Version: 6.1.0 (candidate)
+Revision: efdf8385488430cb3fc15a37ca284c4e2ea1b97f
+Date: July 19 2017
 License: BSD
 
-
 Description:
-This directory contains the d8 binaries for Windows, Mac and Linux.
+This directory contains hashes of the d8 binaries for Windows, Mac and Linux.
+The files are stored in cloud storage in the bucket dart-dependencies,
+and are downloaded by the depot_tools tool download_from_cloud_storage.py.
 The files were fetched from the v8 builders on the DartFYI waterfall:
 http://build.chromium.org/p/client.dart.fyi/console
+The Mac binary is not yet updated, and is at version 4.4.
+Issue: https://github.com/dart-lang/sdk/issues/29794
+
 The binaries are used for testing dart code compiled to javascript.