Fix build in QWebEnginePage API test

Change-Id: I7cb497ce0f67eaf948caa88930fa1a3040ff4c39
Reviewed-by: Andras Becsi <andras.becsi@digia.com>
Merge remote-tracking branch 'origin/5.4' into 5.4.0

Change-Id: I3b7df1ada08a8985734d804208b50cd5e0403903
Add a stub AccessTokenStore implementation.

Callers inside Chromium expect an implementation of AccessTokenStore to exist.
This fixes crashes with the geolocation-based APIs, exposed on e.g. google.com
when faking an Android UA (as well as other places, probably).

Change-Id: I45e6b483e096d5165fefd86927cdf34e799cc4d9
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>