diff --git a/services/surfaceflinger/DispSync.h b/services/surfaceflinger/DispSync.h
index c2ae135..5826a78 100644
--- a/services/surfaceflinger/DispSync.h
+++ b/services/surfaceflinger/DispSync.h
@@ -83,7 +83,7 @@
     bool addResyncSample(nsecs_t timestamp);
     void endResync();
 
-    // The setPreiod method sets the vsync event model's period to a specific
+    // The setPeriod method sets the vsync event model's period to a specific
     // value.  This should be used to prime the model when a display is first
     // turned on.  It should NOT be used after that.
     void setPeriod(nsecs_t period);
@@ -102,6 +102,12 @@
     // DispSync object.
     status_t removeEventListener(const sp<Callback>& callback);
 
+    // computeNextRefresh computes when the next refresh is expected to begin.
+    // The periodOffset value can be used to move forward or backward; an
+    // offset of zero is the next refresh, -1 is the previous refresh, 1 is
+    // the refresh after next. etc.
+    nsecs_t computeNextRefresh(int periodOffset) const;
+
 private:
 
     void updateModelLocked();