Add common code for extensions event filtering.

chrome/common/extensions/event_matcher.cc

+// Copyright (c) 2012 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 "chrome/common/extensions/event_matcher.h"
+#include "chrome/common/extensions/event_filtering_info.h"
+
+namespace extensions {
+
+EventMatcher::EventMatcher() {
+}
+
+EventMatcher::~EventMatcher() {
+}
+
+bool EventMatcher::MatchNonURLCriteria(
+    const EventFilteringInfo& event_info) const {
+  // There is currently no criteria apart from URL criteria.
+  return true;
+}
+
+}  // namespace extensions