Add AssertNoURLRequests() to URLRequestContext subclass destructors.

net/url_request/url_request_context.h

 // 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.
 
 // This class represents contextual information (cookies, cache, etc.)
 // that's useful when processing resource requests.
 // The class is reference-counted so that it can be cleaned up after any
 // requests that are using it have been completed.
 
 #ifndef NET_URL_REQUEST_URL_REQUEST_CONTEXT_H_
@@ skipping 181 matching lines @@
   void set_sdch_manager(SdchManager* sdch_manager) {
     sdch_manager_ = sdch_manager;
   }
 
   // Gets the URLRequest objects that hold a reference to this
   // URLRequestContext.
   std::set<const URLRequest*>* url_requests() const {
     return url_requests_.get();
   }
 
+  // CHECKs that no URLRequests using this context remain. Subclasses should
+  // additionally call AssertNoURLRequests() within their own destructor,
+  // prior to implicit destruction of subclass-owned state.

[sky, 2014/07/10 19:37:32]

How come the call to this in the destructor isn't enough?

[Ryan Sleevi, 2014/07/10 19:39:36]

The issue is running into crashes in the derived-classes due to URLRequests
still living, for which their DTORs run before the base class (which calls this)

By moving it into the derived classes (as well), this avoids even more
mysterious crash debugging and making the culprit explicit.

   void AssertNoURLRequests() const;
 
   // Get the underlying |HttpUserAgentSettings| implementation that provides
   // the HTTP Accept-Language and User-Agent header values.
   const HttpUserAgentSettings* http_user_agent_settings() const {
     return http_user_agent_settings_;
   }
   void set_http_user_agent_settings(
       HttpUserAgentSettings* http_user_agent_settings) {
     http_user_agent_settings_ = http_user_agent_settings;
@@ skipping 32 matching lines @@
   // ---------------------------------------------------------------------------
 
   scoped_ptr<std::set<const URLRequest*> > url_requests_;
 
   DISALLOW_COPY_AND_ASSIGN(URLRequestContext);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_CONTEXT_H_