trace: [tracetool] Minimize the amount of per-backend code

Backends now only contain the essential backend-specific code, and most of the work is moved to frontend code.

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/scripts/simpletrace.py b/scripts/simpletrace.py
index b9aeb56..800835a 100755
--- a/scripts/simpletrace.py
+++ b/scripts/simpletrace.py
@@ -109,14 +109,10 @@
     if isinstance(log, str):
         log = open(log, 'rb')
 
-    enabled_events = []
     dropped_event = Event.build("Dropped_Event(uint64_t num_events_dropped)")
     edict = {dropped_event_id: dropped_event}
 
-    for e in events:
-        if 'disable' not in e.properties:
-            enabled_events.append(e)
-    for num, event in enumerate(enabled_events):
+    for num, event in enumerate(events):
         edict[num] = event
 
     def build_fn(analyzer, event):