hwc: Calculate true rendering area to be blitted using MDP

Though we receive request for more area to be rendered, after
different optimizations we end up rendering lesser in many cases.
Right now we are considering requested rendering area to take
composition decision. Including calculation of true rendering area
will increase scope of MDP for more use-cases with out effecting
its limitation of dynamic threshold 1.5

Change-Id: Ibcf6ba943d418c6c46e2b08d73a212e4cfb6179c
diff --git a/libhwcomposer/hwc_copybit.h b/libhwcomposer/hwc_copybit.h
index 993c790..0d05dd9 100644
--- a/libhwcomposer/hwc_copybit.h
+++ b/libhwcomposer/hwc_copybit.h
@@ -141,6 +141,7 @@
                   int dpy);
     bool isLayerChanging(hwc_context_t *ctx,
                             hwc_display_contents_1_t *list, int k);
+    bool isSmartBlitPossible(const hwc_display_contents_1_t *list);
 };
 
 }; //namespace qhwc