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.cpp b/services/surfaceflinger/Layer.cpp
index 0825ec6..4c82f91 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -50,9 +50,8 @@
 
 // ---------------------------------------------------------------------------
 
-Layer::Layer(SurfaceFlinger* flinger,
-        DisplayID display, const sp<Client>& client)
-    :   LayerBaseClient(flinger, display, client),
+Layer::Layer(SurfaceFlinger* flinger, const sp<Client>& client)
+    :   LayerBaseClient(flinger, client),
         mTextureName(-1U),
         mQueuedFrames(0),
         mCurrentTransform(0),