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

components/sync/engine_impl/cycle/nudge_tracker.h

Index: components/sync/engine_impl/cycle/nudge_tracker.h
diff --git a/components/sync/engine_impl/cycle/nudge_tracker.h b/components/sync/engine_impl/cycle/nudge_tracker.h
index 5bd69c9259e534d766b8cba42a394f87005818b9..1840f5c2ba092937aa644922341a84ee73c0e14c 100644
--- a/components/sync/engine_impl/cycle/nudge_tracker.h
+++ b/components/sync/engine_impl/cycle/nudge_tracker.h
@@ -84,22 +84,43 @@ class NudgeTracker {
                               base::TimeDelta length,
                               base::TimeTicks now);
 
-  // Removes any throttling that have expired by time |now|.
-  void UpdateTypeThrottlingState(base::TimeTicks now);
+  // Marks |type| as being backed off from |now| until |now| + |length|.
+  void SetTypeBackedOff(ModelType type,
+                        base::TimeDelta length,
+                        base::TimeTicks now);
+
+  // Removes any throttling and backoff that have expired by time |now|.
+  void UpdateTypeThrottlingAndBackoffState(base::TimeTicks now);
 
   // Returns the time of the next type unthrottling, relative to
   // the input |now| value.
   base::TimeDelta GetTimeUntilNextUnthrottle(base::TimeTicks now) const;
 
+  // Returns the time of the next type unbackoff, relative to
+  // the input |now| value.
+  base::TimeDelta GetTimeUntilNextUnbackoff(base::TimeTicks now) const;
+
+  // Returns the time of for type last backing off interval.
+  base::TimeDelta GetTypeLastBackoffInterval(ModelType type) const;
+
   // Returns true if any type is currenlty throttled.
   bool IsAnyTypeThrottled() const;
 
+  // Returns true if any type is currenlty backed off.
+  bool IsAnyTypeBackedOff() const;
+
   // Returns true if |type| is currently throttled.
   bool IsTypeThrottled(ModelType type) const;
 
+  // Returns true if |type| is currently backed off.
+  bool IsTypeBackedOff(ModelType type) const;
+
   // Returns the set of currently throttled types.
   ModelTypeSet GetThrottledTypes() const;
 
+  // Returns the set of currently backed off types.
+  ModelTypeSet GetBackedOffTypes() const;
+
   // Returns the set of types with local changes pending.
   ModelTypeSet GetNudgedTypes() const;