reimplement wifi display hack with new external display SF framework

fix a few bugs with external displays

- HWComposer doesn't really handle multiple displays yet
  so there is a lot of ugliness there

- We also need to make sure that external displays are not
  blanked by default

- due to some EGL limitations surfaces being swapped need
  to be current

Change-Id: I82bff05b43bcebd8da863c7c76b4edbc3bc223a9
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 6438bee..4831d9d 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -428,9 +428,7 @@
      * Feature prototyping
      */
 
-    EGLSurface getExternalDisplaySurface() const;
-    sp<SurfaceTextureClient> mExternalDisplayNativeWindow;
-    EGLSurface mExternalDisplaySurface;
+    sp<IBinder> mExtDisplayToken;
 };
 
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