Determine displayType in SurfaceFlinger

This change eliminates an assumption that the first hotplug connect
event is for the primary display, and all other events are for the
external display.

Bug: 38464421
Test: Boots, settings app navigable
Change-Id: I753deb9a4e99a7b225ab89562c7acf4ce284dbf5
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index 74b3a38..ee0a725 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -136,7 +136,7 @@
     // DisplayDevice::DisplayType of the display is returned as an output param.
     bool onVsync(hwc2_display_t displayId, int64_t timestamp,
                  int32_t* outDisplay);
-    void onHotplug(hwc2_display_t displayId, HWC2::Connection connection);
+    void onHotplug(hwc2_display_t displayId, int32_t displayType, HWC2::Connection connection);
 
     void setVsyncEnabled(int32_t displayId, HWC2::Vsync enabled);