Add AssertNoURLRequests() to URLRequestContext subclass destructors.

net/url_request/url_request_context.h

Index: net/url_request/url_request_context.h
diff --git a/net/url_request/url_request_context.h b/net/url_request/url_request_context.h
index 4242d72e6d9fed313c325313996f0deb1841d5e8..fe4213a437d85c28eda0037319a928bf5b9a0d41 100644
--- a/net/url_request/url_request_context.h
+++ b/net/url_request/url_request_context.h
@@ -199,6 +199,9 @@ class NET_EXPORT URLRequestContext
     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