[Background loader] .h file draft outline of background loader

components/background_loader/background_loader_contents.h

+// Copyright (c) 2016 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 COMPONENTS_BACKGROUND_LOADER_BACKGROUND_LOADER_CONTENTS_H_
+#define COMPONENTS_BACKGROUND_LOADER_BACKGROUND_LOADER_CONTENTS_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_delegate.h"
+#include "content/public/browser/web_contents_observer.h"
+#include "url/gurl.h"
+
+namespace background {
+
+typedef base::Callback<void(content::WebContents*)> WebContentsCallback;

[Dmitry Titov, 2016/10/06 04:36:02]

I wonder why you need to give the WebContents out like this, since I think the
caller of LoadPage has (owns?) an instance of this class and can always call
web_contents() from it. 

Perhaps you meant the callback as a signal that load ended?

Happy to chat more in the office!

[chili, 2016/10/12 20:57:30]

I was playing around with different ways to offer up the internal web contents. 
After the discussion during last week's meeting, it makes more sense to have
observer rather than a callback type structure for when to take the snapshot.

+
+// This class maintains a WebContents used in the background. It can host
+// a renderer but does not have any visible display.
+class BackgroundLoaderContents : public content::WebContentsDelegate,
+                                 public content::WebContentsObserver {
+ public:
+  BackgroundLoaderContents(
+      content::BrowserContext* browser_context,
+      content::SessionStorageNamespace* session_storage_namespace);
+  BackgroundLoaderContents(content::BrowserContext* browser_context);
+  ~BackgroundLoaderContents() override;
+
+  content::WebContents* web_contents() const { return web_contents_.get(); }
+  void LoadPage(const GURL& url, const WebContentsCallback& callback);

[Dmitry Titov, 2016/10/06 04:36:02]

How do you plan to communicate  the progress of that load to the user of this
class? Some sort of Observer interface?

[chili, 2016/10/12 20:57:30]

Added an observer class for this.  I originally followed what the prerendering
loader was doing, which essentially just says that we only need to know when the
page load is done.  Integrating snapshot controller and possibly taking multiple
snapshots at different points in time made observer a much better choice

+  void StopLoading();
+
+  // content::WebContentsDelegate Implementation:
+  void CloseContents(content::WebContents* source) override;
+  bool ShouldSuppressDialogs(content::WebContents* source) override;
+  bool IsNeverVisible(content::WebContents* web_contents) override;
+  bool ShouldFocusLocationBarByDefault(content::WebContents* source) override;
+  bool ShouldFocusPageAfterCrash() override;
+  void CanDownload(const GURL& url,
+                   const std::string& request_method,
+                   const base::Callback<void(bool)>& callback) override;
+  bool ShouldCreateWebContents(
+      content::WebContents* contents,
+      int32_t route_id,
+      int32_t main_frame_route_id,
+      int32_t main_frame_widget_route_id,
+      WindowContainerType window_container_type,
+      const std::string& frame_name,
+      const GURL& target_url,
+      const std::string& partition_id,
+      content::SessionStorageNamespace* session_storage_namespace) override;
+  void RequestMediaAccessPermission(
+      content::WebContents* contents,
+      const content::MediaStreamRequest& request,
+      const content::MediaResponseCallback& callback) override;
+  bool CheckMediaAccessPermission(content::WebContents* contents,
+                                  const GURL& security_origin,
+                                  content::MediaStreamType type) override;
+
+  // content::WebContentsObserver Implementation:
+  void RenderProcessGone(base::TerminationStatus status) override;
+  void DidStartLoading() override;
+  void DidStopLoading() override;
+
+ protected:
+  BackgroundLoaderContents();
+
+ private:
+  Profile* profile_;
+  std::unique_ptr<content::WebContents> web_contents_;
+  content::SessionStorageNamespaceMap session_storage_namespace_map_;
+  content::BrowserContext* browser_context_;

[Dmitry Titov, 2016/10/06 04:36:02]

BrowserContext and Profiel are practically the same thing, you only need one of
those. I think in components folder you can't refer to Profile...

[chili, 2016/10/12 20:57:30]

removed.

+  WebContentsCallback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(BackgroundLoaderContents);
+};
+
+}  // namespace background
+#endif  // COMPONENTS_BACKGROUND_LOADER_BACKGROUND_LOADER_CONTENTS_H_