refactor things a bit

- decouple GL and main display initialization
- ensure that each "supported" display has its own FramebufferSurface
- onScreenAcquired/Released now takes a display

Change-Id: If34a05f3dea40f6c79db77f4dde283a2580daac4
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index 552d42f..fe928c5 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -106,6 +106,10 @@
     // needed forward declarations
     class LayerListIterator;
 
+    // return the visual id to be used to find a suitable EGLConfig for
+    // *ALL* displays.
+    int getVisualID() const;
+
     // Forwarding to FB HAL for pre-HWC-1.1 code (see FramebufferSurface).
     int fbPost(buffer_handle_t buffer);
     int fbCompositionComplete();