Bug 1011469 - Intermittent in cost control tests, tapping Next button has no effect
Merge pull request #19595 from viorelaioia/bug_1011469

Bug 1011469 - Intermittent in cost control tests, tapping Next button has no effect
Bug 1013295 - [Messages] Migrated messages do not have a proper sentTimestamp. Hiding label with invalid timestamp. r=schung
Fixed nits: removed invalid 'timestamp' property case handling + added fake message with invalid 'sentTimestamp' to make it easier to test on desktop.