SF: Set state modified flag when changing sizes

The BufferRejecter updates the Layer state when it gets the first
buffer of the new size after a size change has occurred. When this
happens make sure to set the state modified flag.

Bug 27780983

Change-Id: Id8c628c40164110e75f8defd68ca895d72ed2e83
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 96252f3..ed320cb 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -1820,6 +1820,7 @@
                         // NOTE: We don't need to hold the transaction lock here
                         // because State::active is only accessed from this thread.
                         current.active = front.active;
+                        current.modified = true;
 
                         // recompute visible region
                         recomputeVisibleRegions = true;