hwcomposer: Add support for UI mirroring

- Uevent observer as part of Hwcomposer
- HPD, enabling/disabling external display from HWC

Change-Id: I52b4f30c78e98c5b52c86722046389f458c2dbee
diff --git a/liboverlay/overlayUtils.cpp b/liboverlay/overlayUtils.cpp
index 8c9ca99..ce18174 100644
--- a/liboverlay/overlayUtils.cpp
+++ b/liboverlay/overlayUtils.cpp
@@ -142,7 +142,10 @@
 }
 
 bool FrameBufferInfo::supportTrueMirroring() const {
-    return mBorderFillSupported;
+    char value[PROPERTY_VALUE_MAX] = {0};
+    property_get("hw.trueMirrorSupported", value, "0");
+    int trueMirroringSupported = atoi(value);
+    return (trueMirroringSupported && mBorderFillSupported);
 }
 
 //--------------------------------------------------------