surfaceflinger: remove DisplayDevice::swapRegion

With SWAP_RECTANGLE and PARTIAL_UPDATES removed, it becomes clear
that swapRegion is not needed.  It also becomes clear that
DisplayDevice::flip and SurfaceFlinger::doComposeSurfaces do not
need the dirty region.

Test: SurfaceFlinger_test
Change-Id: Id9cd2b43812d3c7dcfa36f605d0f8a647264f228
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 58d9998..974de94 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -543,7 +543,7 @@
 
     // compose surfaces for display hw. this fails if using GL and the surface
     // has been destroyed and is no longer valid.
-    bool doComposeSurfaces(const sp<const DisplayDevice>& displayDevice, const Region& dirty);
+    bool doComposeSurfaces(const sp<const DisplayDevice>& displayDevice);
 
     void postFramebuffer();
     void drawWormhole(const sp<const DisplayDevice>& displayDevice, const Region& region) const;