PlzNavigate: Add first version of NavigationURLLoader.

content/browser/loader/navigation_url_loader_delegate.h

+// Copyright 2014 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_BROWSER_LOADER_NAVIGATION_URL_LOADER_DELEGATE_H_
+#define CONTENT_BROWSER_LOADER_NAVIGATION_URL_LOADER_DELEGATE_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "content/common/content_export.h"
+
+namespace net {
+struct RedirectInfo;
+}
+
+namespace content {
+
+class StreamHandle;
+struct ResourceResponse;
+
+// PlzNavigate: The delegate interface to NavigationURLLoader.
+class CONTENT_EXPORT NavigationURLLoaderDelegate {
+ public:
+  // Called when the request is redirected. Call FollowRedirect to continue
+  // processing the request.
+  virtual void OnRequestRedirected(const net::RedirectInfo& redirect_info,
+                                   ResourceResponse* response) = 0;

[mmenke, 2014/10/28 16:05:39]

Suggest making this a "const scoped_refptr&".  That makes ownership semantics
much clearer.

[davidben, 2014/10/29 19:10:34]

Done. At least within loader/.

+
+  // Called when the request receives its response. No further calls will be
+  // made to the delegate. The response body is returned as a stream in
+  // |body|.
+  virtual void OnResponseStarted(ResourceResponse* response,
+                                 scoped_ptr<StreamHandle> body) = 0;

[mmenke, 2014/10/28 16:05:39]

nit:  Maybe body_stream?  Or body_blob?  Or bloby_body_stream or something.

[davidben, 2014/10/29 19:10:33]

*shrug* I feel like body is pretty descriptive. StreamHandle just happens to be
the mechanism we currently use to convey the body, but it won't be that forever.
Should it then be renamed to body_data_pipe or whatever? frame_host is already
calling it plain |body| and renaming it from |body_stream| to |body| partway
through seems confusing. (And part of the point of landing the frame_host
changes earlier was so this CL doesn't keep growing...)

[mmenke, 2014/10/29 19:44:46]

I dunno...  I see a test mucking with something called "body", and I think "Oh,
that's a string", not "Oh, now that we have the body in an in-memory object, we
have to issue a URLRequest to it in order to read from it while spinning the
message loop before we can make sure everything's peachy".

[davidben, 2014/10/29 19:46:54]

Yeah, that a StreamHandle requires a URLRequest to cash in on it is kind of
unfortunate and why we'll be changing this to something better later. This is
just to let PlzNavigate progress without rewriting all of Blink's navigation
code. :-)

+
+  // Called if the request fails before receving a response. |net_error| is a
+  // network error code for the failure.
+  virtual void OnRequestFailed(int net_error) = 0;
+
+ protected:
+  NavigationURLLoaderDelegate() {}
+  virtual ~NavigationURLLoaderDelegate() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(NavigationURLLoaderDelegate);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_LOADER_NAVIGATION_URL_LOADER_DELEGATE_H_