Remove unused "layer" argument from show().

Change-Id: I8944a9f4a27c330b11e5e837c69b88c8f84145ba
diff --git a/include/gui/Surface.h b/include/gui/Surface.h
index 6f2d40f..2288fe7 100644
--- a/include/gui/Surface.h
+++ b/include/gui/Surface.h
@@ -65,7 +65,7 @@
     status_t    setPosition(int32_t x, int32_t y);
     status_t    setSize(uint32_t w, uint32_t h);
     status_t    hide();
-    status_t    show(int32_t layer = -1);
+    status_t    show();
     status_t    setFlags(uint32_t flags, uint32_t mask);
     status_t    setTransparentRegionHint(const Region& transparent);
     status_t    setAlpha(float alpha=1.0f);