Bug 855765 - Move test_bug_795164 to dom/apps and avoid UI confirmation. r=fabrice, a=test-only

--HG--
rename : dom/apps/tests/test_uninstall_errors.html => dom/apps/tests/test_bug_795164.html
Bug 913983 - Split browser_telemetry_buttonsandsidebar.js into 5 tests due to timeouts. r=jwalker, a=test-only
Bug 896067 - Icons for guest sessions. r=sriram, a=akeybl
Bug 917515 - Check for null before checking the document. r=ehsan, a=akeybl
Bug 921023 - Properly re-enable mixed content blocking. r=mfinkle, a=akeybl
Bug 911695 - Use correct dppx values for HDPI and XHDPI devices. r=margaret, a=akeybl