Merge pull request #8134 from albertopq/contacts-list-performance

Bug 835742 - [Contacts] Improve contacts list rendering performance r=arcturus(cherry picked from commit d57cca775b5f2c522d8f0eafd7559f3874f6c7b5)

Conflicts:
	apps/communications/contacts/js/contacts_list.js
	apps/communications/contacts/test/performance/rendering_test.js
	apps/communications/contacts/test/unit/contacts_list_test.js
	apps/communications/contacts/test/unit/mock_fb.js
Merge bug 835742 to v1-train