We now report hotplug events to the framework

Change-Id: I2d6b7787d39e5929485a551e4982498c5053c211
diff --git a/include/gui/DisplayEventReceiver.h b/include/gui/DisplayEventReceiver.h
index e631cca..1117f95 100644
--- a/include/gui/DisplayEventReceiver.h
+++ b/include/gui/DisplayEventReceiver.h
@@ -40,7 +40,8 @@
 class DisplayEventReceiver {
 public:
     enum {
-        DISPLAY_EVENT_VSYNC = 'vsyn'
+        DISPLAY_EVENT_VSYNC = 'vsyn',
+        DISPLAY_EVENT_HOTPLUG = 'plug'
     };
 
     struct Event {
@@ -54,9 +55,15 @@
             uint32_t count;
         };
 
+        struct Hotplug {
+            int32_t id;
+            bool connected;
+        };
+
         Header header;
         union {
             VSync vsync;
+            Hotplug hotplug;
         };
     };