Fix classes that have too many virtuals for inline constructors.

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 {
@@ skipping 30 matching lines @@
   virtual void BrowserChildProcessKilled(const ChildProcessData& data,
                                          int exit_code) {}
 
   // 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:
+  BrowserChildProcessObserver() = default;
   // 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_