The user has the option to go to 'Shortcuts' -> 'Search engine settings' to
modify the default search engine. When returning from that settings screen we
need to update it to account for any changes.
For this we will check the current default engine against a previously stored
value in a newly added 'defaultEngineSource' property from SearchState class.
Also, I modified 'SearchStoreTest' by adding the new parameter to the
'SearchState' constructor.

* Created new craft method + decision task call + bug 1558456 logic

* Created new craft method + decision task call + bug 1558456 logic

Sent an announcement when the list becomes empty in order to tell the user
that there is no history.

Closes #4102 - Upgrade Leanplum version from 4.3.1 to 5.2.3

This reverts commit bd9ff938e79b0cabc5a142f18503284c3dfa3e4d.

Do not notify the perf sheriff team anymore when the raptor decision task fails. Also be clearer about who should look into the failure first

* For #4199 make checkbox unclickable when there is no data