Re-enable empty damage drop optimization

Fixes: 113796161
Test: device seemed to behave correctly?
Change-Id: Id43e1eaad29d07c06c1003c0653e5d1ee7084cfe
diff --git a/libs/hwui/renderthread/CanvasContext.h b/libs/hwui/renderthread/CanvasContext.h
index db97763..4da0eac 100644
--- a/libs/hwui/renderthread/CanvasContext.h
+++ b/libs/hwui/renderthread/CanvasContext.h
@@ -217,6 +217,7 @@
     void freePrefetchedLayers();
 
     bool isSwapChainStuffed();
+    bool surfaceRequiresRedraw();
 
     SkRect computeDirtyRect(const Frame& frame, SkRect* dirty);