content: convert child process notifications to observer usage

content/public/browser/browser_child_process_observer.h

+// Copyright 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.
+
+#ifndef CONTENT_PUBLIC_BROWSER_BROWSER_CHILD_PROCESS_OBSERVER_H_
+#define CONTENT_PUBLIC_BROWSER_BROWSER_CHILD_PROCESS_OBSERVER_H_
+
+#include "content/common/content_export.h"
+
+namespace content {
+
+struct ChildProcessData;
+
+// An observer API implemented by classes which are interested
+// in browser child process events.
+class CONTENT_EXPORT BrowserChildProcessObserver {
+ public:
+  // Called when a child process host has connected to a child process.
+  virtual void BrowserChildProcessHostConnected(const ChildProcessData& data) {}
+
+  // Called after a ChildProcessHost is disconnected from the child process.
+  virtual void BrowserChildProcessHostDisconnected(
+      const ChildProcessData& data) {}
+
+  // Called when a child process disappears unexpectedly as a result of a crash.
+  virtual void BrowserChildProcessCrashed(const ChildProcessData& data) {}
+
+  // Called when an instance of a particular child is created in a page. If one
+  // page contains several regions rendered by the same child, this will be
+  // called once for each region during the page load.
+  virtual void BrowserChildProcessInstanceCreated(
+      const ChildProcessData& data) {}
+
+ protected:
+  // The observer can be destroyed on any thread.
+  virtual ~BrowserChildProcessObserver() {}
+
+  static void Add(BrowserChildProcessObserver* observer);
+  static void Remove(BrowserChildProcessObserver* observer);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_BROWSER_CHILD_PROCESS_OBSERVER_H_