Eradicate DisplayID.

DisplayDevices are now keyed of the wp<IBinder> the client uses.
DisplayID has now become DisplayType which is just used to identify
physical displays (as opposed to virtual displays such as wifi displays).

Change-Id: I0c5968f2c902dcd699a7e0afacf833ff070c12ea
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index d24013b..78fe321 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -50,9 +50,7 @@
 class Layer : public LayerBaseClient
 {
 public:
-            Layer(SurfaceFlinger* flinger, DisplayID display,
-                    const sp<Client>& client);
-
+            Layer(SurfaceFlinger* flinger, const sp<Client>& client);
     virtual ~Layer();
 
     virtual const char* getTypeId() const { return "Layer"; }