Merge to XFA: Introduce kPerIsolateDataIndex and tidy JS_Define.h

(cherry picked from commit d6d9dc6b9a45368abdf43477592ee9f6cdb6102e)
(cherry picked from commit cfff2f65aaec70247d020188bc68a0dc4fb34c3e)

Original Review URL: https://codereview.chromium.org/1372963003 .
Original Review URL: https://codereview.chromium.org/1367813003 .

TBR=jochen@chromium.org

Review URL: https://codereview.chromium.org/1370133007 .
diff --git a/DEPS b/DEPS
index 3103fff..534bb97 100644
--- a/DEPS
+++ b/DEPS
@@ -15,7 +15,7 @@
      "https://chromium.googlesource.com/external/googletest.git@8245545b6dc9c4703e6496d1efd19e975ad2b038",
 
   "v8":
-    "https://chromium.googlesource.com/v8/v8.git",
+    "https://chromium.googlesource.com/v8/v8.git@4d03c3aabad6517ff058124bb799ca6a4156e570",
 
   "v8/third_party/icu":
     "https://chromium.googlesource.com/chromium/deps/icu46",