Remove support for a URLRequest having a NULL Delegate.

net/url_request/url_request.h

Index: net/url_request/url_request.h
diff --git a/net/url_request/url_request.h b/net/url_request/url_request.h
index f1d90edb558fe1f40a5b2c61c2be0c9f7576dc36..91aad84cd65eca3612b6bf44158a37cde47090db 100644
--- a/net/url_request/url_request.h
+++ b/net/url_request/url_request.h
@@ -303,8 +303,9 @@ class NET_EXPORT URLRequest : NON_EXPORTED_BASE(public base::NonThreadSafe),
   ReferrerPolicy referrer_policy() const { return referrer_policy_; }
   void set_referrer_policy(ReferrerPolicy referrer_policy);
 
-  // Sets the delegate of the request.  This value may be changed at any time,
-  // and it is permissible for it to be null.
+  // Sets the delegate of the request.  This is only to allow creating a request
+  // before creating its delegate.  |delegate| must be non-NULL and the request
+  // must not yet have a Delegate set.
   void set_delegate(Delegate* delegate);
 
   // Indicates that the request body should be sent using chunked transfer
@@ -522,8 +523,9 @@ class NET_EXPORT URLRequest : NON_EXPORTED_BASE(public base::NonThreadSafe),
   // Returns a globally unique identifier for this request.
   uint64 identifier() const { return identifier_; }
 
-  // This method is called to start the request.  The delegate will receive
-  // a OnResponseStarted callback when the request is started.
+  // This method is called to start the request.  The Delegate will receive
+  // a OnResponseStarted callback when the request is started.  The request
+  // must have a delegate set before this method is called.

[xunjieli, 2015/12/14 20:12:08]

nit: maybe s/delegate/Delegate to be consistent with the first instance of this
word in this comment.

[mmenke, 2015/12/14 20:24:11]

I decided to go with "delegate" in both places instead.  I think Delegate is
better, when we mean URLRequest::Delegate only and not NetworkDelegate, but this
file uses "delegate" almost everywhere.  May fix it in another CL, but too many
places to fix in this CL, I think.

   void Start();
 
   // This method may be called at any time after Start() has been called to
@@ -621,9 +623,6 @@ class NET_EXPORT URLRequest : NON_EXPORTED_BASE(public base::NonThreadSafe),
   // due to HSTS. If so, |redirect_url| is rewritten to the new HTTPS URL.
   bool GetHSTSRedirect(GURL* redirect_url) const;
 
-  // TODO(willchan): Undo this. Only temporarily public.
-  bool has_delegate() const { return delegate_ != NULL; }
-
   // NOTE(willchan): This is just temporary for debugging
   // http://crbug.com/90971.
   // Allows to setting debug info into the URLRequest.