PlzNavigate: Add first version of NavigationURLLoader.

content/browser/loader/navigation_url_loader.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_H_
+#define CONTENT_BROWSER_LOADER_NAVIGATION_URL_LOADER_H_
+
+#include "base/basictypes.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "content/common/content_export.h"
+
+namespace net {
+struct RedirectInfo;
+}
+
+namespace content {
+
+class BrowserContext;
+class NavigationURLLoaderFactory;
+class StreamHandle;
+class ResourceRequestBody;
+struct CommonNavigationParams;
+struct NavigationRequestInfo;
+struct ResourceResponse;
+
+// PlzNavigate: The navigation logic's UI thread entry point into the resource
+// loading stack. It exposes an interface to control the request prior to
+// receiving the response. If the NavigationURLLoader is destroyed before
+// OnResponseStarted is called, the request is aborted.
+class CONTENT_EXPORT NavigationURLLoader {
+ public:
+  class CONTENT_EXPORT Delegate {

[mmenke, 2014/10/22 15:32:58]

I believe that there's a preference to make delegates/observers separate
top-level classes, rather than nesting them like this.

[davidben, 2014/10/22 20:58:04]

Done. (Another file? Fine.)

+   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;
+
+    // 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;
+
+    // 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:
+    Delegate() {}
+    virtual ~Delegate() {}
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(Delegate);
+  };
+
+  // Creates a NavigationURLLoader. The caller is responsible for ensuring that
+  // |delegate| outlives the loader. |request_body| must not be accessed on the
+  // UI thread after this point.
+  //
+  // TODO(davidben): When navigation is disentangled from the loader, the
+  // request parameters should not come in as a navigation-specific
+  // structure. Information like has_user_gesture and
+  // should_replace_current_entry shouldn't be needed at this layer.
+  static scoped_ptr<NavigationURLLoader> Create(
+      BrowserContext* browser_context,
+      int64 frame_tree_node_id,
+      const CommonNavigationParams& common_params,
+      scoped_ptr<NavigationRequestInfo> request_info,
+      ResourceRequestBody* request_body,
+      Delegate* delegate);
+
+  // For testing purposes; sets the factory for use in testing.
+  static void SetFactoryForTesting(NavigationURLLoaderFactory* factory);
+
+  virtual ~NavigationURLLoader() {}
+
+  // Called in response to OnRequestRedirected to continue processing the
+  // request.
+  virtual void FollowRedirect() = 0;
+
+protected:

[mmenke, 2014/10/22 15:32:58]

nit:  +1 indent, here and below.

[davidben, 2014/10/22 20:58:04]

Done. Huh, I wonder why emacs is failing me here...

+  NavigationURLLoader() {}
+
+private:
+  DISALLOW_COPY_AND_ASSIGN(NavigationURLLoader);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_LOADER_NAVIGATION_URL_LOADER_H_