Add the basic code skeleton for system info event router

chrome/browser/extensions/system_info_watcher.cc

Index: chrome/browser/extensions/system_info_watcher.cc
diff --git a/chrome/browser/extensions/system_info_watcher.cc b/chrome/browser/extensions/system_info_watcher.cc
new file mode 100644
index 0000000000000000000000000000000000000000..611a6246e62d70c64544f0c4175e0cf4256cd916
--- /dev/null
+++ b/chrome/browser/extensions/system_info_watcher.cc
@@ -0,0 +1,56 @@
+// 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/browser/extensions/system_info_watcher.h"
+
+#include "base/logging.h"
+
+namespace extensions {
+
+SystemInfoWatcher::SystemInfoWatcher() {
+}
+
+SystemInfoWatcher::~SystemInfoWatcher() {
+}
+
+// static
+void SystemInfoWatcher::InitializeForTesting(SystemInfoWatcher* watcher) {
+  DCHECK(watcher);
+  single_shared_watcher_.Get().reset(watcher);
+}
+
+void SystemInfoWatcher::AddObserver(Observer* observer) {
+  DCHECK(observer);
+  observers_.AddObserver(observer);
+}
+
+void SystemInfoWatcher::RemoveObserver(Observer* observer) {
+  DCHECK(observer);
+  observers_.RemoveObserver(observer);
+}
+
+bool SystemInfoWatcher::StartWatching(const std::string& event_name) {
+  if (IsWatching(event_name))
+    return true;
+  return PlatformStartWatching(event_name);
+}
+
+bool SystemInfoWatcher::StopWatching(const std::string& event_name) {
+  bool success = true;
+  if (IsWatching(event_name)) {
+   success = PlatformStopWatching(event_name);
+   watching_event_names_.erase(event_name);
+  }
+  return success;
+}
+
+bool SystemInfoWatcher::IsWatching(const std::string& event_name) {
+  return watching_event_names_.find(event_name) != watching_event_names_.end();
+}
+
+// The single shared instance initialization.
+base::LazyInstance<scoped_ptr<SystemInfoWatcher> >
+    SystemInfoWatcher::single_shared_watcher_ = LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace extensions