content: convert child process notifications to observer usage

content/public/browser/browser_child_process_observer.cc

Index: content/public/browser/browser_child_process_observer.cc
diff --git a/content/public/browser/browser_child_process_observer.cc b/content/public/browser/browser_child_process_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..74d8e519c646edcaac0aeaea010492d0aef09246
--- /dev/null
+++ b/content/public/browser/browser_child_process_observer.cc
@@ -0,0 +1,19 @@
+// Copyright (c) 2013 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 "content/public/browser/browser_child_process_observer.h"
+
+#include "content/browser/browser_child_process_host_impl.h"
+
+namespace content {
+
+void BrowserChildProcessObserver::StartObservingBrowserChildProcesses() {
+  BrowserChildProcessHostImpl::AddObserver(this);
+}
+
+void BrowserChildProcessObserver::StopObservingBrowserChildProcesses() {
+  BrowserChildProcessHostImpl::RemoveObserver(this);
+}
+
+}  // namespace content