[Sync] Sync client should to exponential backoff when receive partial failure

components/sync/engine_impl/cycle/nudge_tracker.cc

Index: components/sync/engine_impl/cycle/nudge_tracker.cc
diff --git a/components/sync/engine_impl/cycle/nudge_tracker.cc b/components/sync/engine_impl/cycle/nudge_tracker.cc
index cef95f2379a827f22735c7b445a76e35c802db94..0e988002ed96ee148642da15ef90f542a67c66ba 100644
--- a/components/sync/engine_impl/cycle/nudge_tracker.cc
+++ b/components/sync/engine_impl/cycle/nudge_tracker.cc
@@ -189,10 +189,18 @@ void NudgeTracker::SetTypesThrottledUntil(ModelTypeSet types,
   }
 }
 
-void NudgeTracker::UpdateTypeThrottlingState(base::TimeTicks now) {
+void NudgeTracker::SetTypeBackedOff(ModelType type,
+                                    base::TimeDelta length,
+                                    base::TimeTicks now) {
+  TypeTrackerMap::const_iterator tracker_it = type_trackers_.find(type);
+  DCHECK(tracker_it != type_trackers_.end());
+  tracker_it->second->BackoffType(length, now);
+}
+
+void NudgeTracker::UpdateTypeThrottlingAndBackoffState(base::TimeTicks now) {
   for (TypeTrackerMap::const_iterator it = type_trackers_.begin();
        it != type_trackers_.end(); ++it) {
-    it->second->UpdateThrottleState(now);
+    it->second->UpdateThrottleOrBackoffState(now);
   }
 }
 
@@ -206,11 +214,26 @@ bool NudgeTracker::IsAnyTypeThrottled() const {
   return false;
 }
 
+bool NudgeTracker::IsAnyTypeBackedOff() const {
+  for (TypeTrackerMap::const_iterator it = type_trackers_.begin();
+       it != type_trackers_.end(); ++it) {
+    if (it->second->IsBackedOff()) {
+      return true;
+    }
+  }
+  return false;
+}
+
 bool NudgeTracker::IsTypeThrottled(ModelType type) const {
   DCHECK(type_trackers_.find(type) != type_trackers_.end());
   return type_trackers_.find(type)->second->IsThrottled();
 }
 
+bool NudgeTracker::IsTypeBackedOff(ModelType type) const {
+  DCHECK(type_trackers_.find(type) != type_trackers_.end());
+  return type_trackers_.find(type)->second->IsBackedOff();
+}
+
 base::TimeDelta NudgeTracker::GetTimeUntilNextUnthrottle(
     base::TimeTicks now) const {
   DCHECK(IsAnyTypeThrottled()) << "This function requires a pending unthrottle";
@@ -229,6 +252,34 @@ base::TimeDelta NudgeTracker::GetTimeUntilNextUnthrottle(
   return time_until_next_unthrottle;
 }
 
+base::TimeDelta NudgeTracker::GetTimeUntilNextUnbackoff(
+    base::TimeTicks now) const {
+  DCHECK(IsAnyTypeBackedOff()) << "This function requires a pending unbackoff";
+
+  // Return min of GetTimeUntilUnbackoff() values for all IsThrottled() types.
+  base::TimeDelta time_until_next_unbackoff = base::TimeDelta::Max();
+  for (TypeTrackerMap::const_iterator it = type_trackers_.begin();
+       it != type_trackers_.end(); ++it) {
+    if (it->second->IsBackedOff()) {
+      time_until_next_unbackoff = std::min(
+          time_until_next_unbackoff, it->second->GetTimeUntilUnbackoff(now));
+    }
+  }
+  DCHECK(!time_until_next_unbackoff.is_max());
+
+  return time_until_next_unbackoff;
+}
+
+base::TimeDelta NudgeTracker::GetTypeLastBackoffInterval(ModelType type) const {
+  TypeTrackerMap::const_iterator tracker_it = type_trackers_.find(type);
+  if (tracker_it != type_trackers_.end()) {
+    NOTREACHED();
+    return base::TimeDelta::FromSeconds(0);
+  }
+
+  return tracker_it->second->GetLastUnbackoffInterval();
+}
+
 ModelTypeSet NudgeTracker::GetThrottledTypes() const {
   ModelTypeSet result;
   for (TypeTrackerMap::const_iterator it = type_trackers_.begin();
@@ -240,6 +291,17 @@ ModelTypeSet NudgeTracker::GetThrottledTypes() const {
   return result;
 }
 
+ModelTypeSet NudgeTracker::GetBackedOffTypes() const {
+  ModelTypeSet result;
+  for (TypeTrackerMap::const_iterator it = type_trackers_.begin();
+       it != type_trackers_.end(); ++it) {
+    if (it->second->IsBackedOff()) {
+      result.Put(it->first);
+    }
+  }
+  return result;
+}
+
 ModelTypeSet NudgeTracker::GetNudgedTypes() const {
   ModelTypeSet result;
   for (TypeTrackerMap::const_iterator it = type_trackers_.begin();