content: convert child process notifications to observer usage

content/public/browser/browser_child_process_observer.h

+// 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.
+
+#ifndef CONTENT_PUBLIC_BROWSER_BROWSER_CHILD_PROCESS_OBSERVER_H_
+#define CONTENT_PUBLIC_BROWSER_BROWSER_CHILD_PROCESS_OBSERVER_H_
+
+#include "base/basictypes.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 created and destroyed on any thread.
+  BrowserChildProcessObserver() {}
+  virtual ~BrowserChildProcessObserver() {}
+
+  void StartObservingBrowserChildProcesses();

[jam, 2013/02/19 18:07:09]

nit: make these be static methods (see content API wiki), and just call them
Add/Remove

[Paweł Hajdan Jr., 2013/02/20 12:11:42]

Done. It wasn't obvious to me what the document was - could you explicitly link
to it? I've read http://www.chromium.org/developers/content-module/content-api
and http://www.chromium.org/developers/content-module . None of them seems to
mention static methods vs. methods like here.

+  void StopObservingBrowserChildProcesses();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BrowserChildProcessObserver);

[jam, 2013/02/19 18:07:09]

nit: get rid of

[Paweł Hajdan Jr., 2013/02/20 12:11:42]

Done.

+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_BROWSER_CHILD_PROCESS_OBSERVER_H_