Add PERFETTO_DFATAL.

Replace all uses of DCHECK(false) with it.

Change-Id: I95f83cc462d3f7310a54cf1117c32fa04fee32e8
diff --git a/src/ipc/deferred.cc b/src/ipc/deferred.cc
index bed3cc2..5542cd5 100644
--- a/src/ipc/deferred.cc
+++ b/src/ipc/deferred.cc
@@ -61,7 +61,7 @@
 
 void DeferredBase::Resolve(AsyncResult<ProtoMessage> async_result) {
   if (!callback_) {
-    PERFETTO_DCHECK(false);
+    PERFETTO_DFATAL("No callback set.");
     return;
   }
   bool has_more = async_result.has_more();