Bug 969227 - Part 1: handle X-Backoff headers.
Bug 969227 - Part 2: add handleBackoff to TokenServerClientDelegate.
Bug 969227 - Part 3: handle Retry-After and X-Backoff in TokenServerClient.
Review comment: add SyncResponse.getContentType.
Review comment: rename invokeHandleBackoff to notifyBackoff.
Review comment: describing notifyBackoff/handleBackoff.
Bug 969227 - Handle X-Backoff headers. r=nalexander
Bug 969227 - Follow-up: handle both X-Backoff and X-Weave-Backoff in TokenServerClient.
Bug 969227 - Test for TokenServerClient backoff handling.
Bug 969227 - Follow-up: handle both X-Backoff and X-Weave-Backoff in TokenServerClient. r=self
Bug 959833 - Re-land pngcrushed images that were mistakenly undone by e624202c4fdf in Bug 969227. a=borked
Bug 958900 - Pre: correct comment.
Bug 958900 - Pre: fix JavaDoc.
Bug 958900 - Part 1: extract (Prefs)BackoffHandler from Sync 1.1 SyncAdapter.
Bug 958900 - Part 2: rename shouldBackOff to shouldBackOffStorage.
Bug 958900 - Part 3: add SchedulePolicy interface for adjusting how FxAccountSyncAdapter will sync.
Bug 958900 - Part 4: implement backoff and periodic sync scheduling for FxAccountSyncAdapter.
Review comment: simplify PrefsBackoffHandler constructor, standardize on implicit leading dot in PrefsBackoffHandler path.
Review comment: lift shouldSync into the SyncAdapters.
Bug 958900 - Part 5: fix client count handling.