Now, 'queryObjects' takes an optional 'objectGroup' argument,
allowing the frontend to release the response value.

This is important because each call produces a new Array, which
could not be released before.

Bug: chromium:815263
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I18c9a68c4ba45020fce9eea63cb263396a18d498
Reviewed-on: https://chromium-review.googlesource.com/935153
Commit-Queue: Erik Luo <luoe@chromium.org>
Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51938}