Banish DisplayID from the SurfaceFlinger API.

Use only display tokens in the API to refer to new displays.

Don't require the caller to specify the display when creating
a surface (since in general a surface could be shown on
any display).

This is intended to be a minimum change just to update the API.
Note that SurfaceFlinger still uses DisplayID in a few places
internally that might cause some features not to work properly
when there are multiple displays (LayerScreenshot, for example).

Change-Id: I3d91eec2da406eefd97bcd53655d403ad865a7e6
diff --git a/include/gui/Surface.h b/include/gui/Surface.h
index 7b8873a..6f2d40f 100644
--- a/include/gui/Surface.h
+++ b/include/gui/Surface.h
@@ -60,6 +60,7 @@
     // release surface data from java
     void        clear();
     
+    status_t    setLayerStack(int32_t layerStack);
     status_t    setLayer(int32_t layer);
     status_t    setPosition(int32_t x, int32_t y);
     status_t    setSize(uint32_t w, uint32_t h);