Fix issue that could cause offline get()s to wait up to 10 seconds. (#978)

Port of https://github.com/firebase/firebase-js-sdk/pull/592

FSTOnlineStateTracker was reverting to OnlineState Unknown on every stream attempt
rather than remaining Offline once the offline heuristic had been met (i.e. 2
stream failures or 10 seconds). This means that getDocument() requests made while
offline could be delayed up to 10 seconds each time (or until the next backoff
attempt failed).

1 files changed, 3 insertions, 2 deletions

diff --git a/Firestore/Source/Remote/FSTOnlineStateTracker.h b/Firestore/Source/Remote/FSTOnlineStateTracker.h
index a414a18..2521c84 100644
--- a/Firestore/Source/Remote/FSTOnlineStateTracker.h
+++ b/Firestore/Source/Remote/FSTOnlineStateTracker.h
@@ -43,9 +43,10 @@ NS_ASSUME_NONNULL_BEGIN
 @property(nonatomic, weak) id<FSTOnlineStateDelegate> onlineStateDelegate;
 
 /**
- * Called by FSTRemoteStore when a watch stream is started.
+ * Called by FSTRemoteStore when a watch stream is started (including on each backoff attempt).
  *
- * It sets the FSTOnlineState to Unknown and starts the onlineStateTimer if necessary.
+ * If this is the first attempt, it sets the FSTOnlineState to Unknown and starts the
+ * onlineStateTimer.
  */
 - (void)handleWatchStreamStart;