tracing: split trace event filter classes out of TraceLog

base/trace_event/trace_event_filter.cc

Index: base/trace_event/trace_event_filter.cc
diff --git a/base/trace_event/trace_event_filter.cc b/base/trace_event/trace_event_filter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..626529586477d1d1d16f7835c80a916e20b311e8
--- /dev/null
+++ b/base/trace_event/trace_event_filter.cc
@@ -0,0 +1,17 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/trace_event/trace_event_filter.h"
+
+namespace base {
+namespace trace_event {
+
+TraceEventFilter::TraceEventFilter() {}
+TraceEventFilter::~TraceEventFilter() {}
+
+void TraceEventFilter::EndEvent(const char* category_name,

[kraynov, 2016/12/06 18:24:23]

Why not pure virtual?

[Primiano Tucci (use gerrit), 2016/12/07 11:17:47]

to not require classes that implement the filter interface to mandatorily define
this.
This method is only for snoop-mode to "see" the end of duration events (concrete
case: heap profiler) but is not required to implement this in order to implement
a filter interface.

+                                const char* event_name) const {}
+
+}  // namespace trace_event
+}  // namespace base