[LayerTraceGenerator] fix mirrors and rel-z data

Now that we are using the new front end to
generate layers trace, we need to make a few fixes
so we can generate data that's parsable by winscope.

This means use a unique id instead of the layer id to
identify layers.

Test: presubmit
Fixes: 255901752
Change-Id: Ib30f7d8e2a5575803c455f947a1fd671095ea7e0
diff --git a/services/surfaceflinger/layerproto/layers.proto b/services/surfaceflinger/layerproto/layers.proto
index 3598308..e9add2e 100644
--- a/services/surfaceflinger/layerproto/layers.proto
+++ b/services/surfaceflinger/layerproto/layers.proto
@@ -138,6 +138,8 @@
   float requested_corner_radius = 56;
 
   RectProto destination_frame = 57;
+
+  uint32 original_id = 58;
 }
 
 message PositionProto {