ES2017 draft 19.1.3.6: If @@toStringTag is not a string, Object.prototype.toString()
returns [object Object], except in the following cases:
 - Array
 - String
 - Arguments
 - Function
 - Error
 - Boolean
 - Number
 - Date
 - RegExp.

For anything else, e.g., Maps, Sets, TypedArrays, or the global object, toString() returns
[object Object] if @@toStringTag is absent or not a string. In order to be able to
easily identify the global object in d8, we set @@toStringTag to "global"
for d8.

CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel
BUG=

Review-Url: https://codereview.chromium.org/2071343002
Cr-Commit-Position: refs/heads/master@{#37218}