Adds shells of classes (PrerenderingOffliner and PrerenderingLoader) to intergrate from Background …

chrome/browser/android/offline_pages/prerendering_loader.h

Index: chrome/browser/android/offline_pages/prerendering_loader.h
diff --git a/chrome/browser/android/offline_pages/prerendering_loader.h b/chrome/browser/android/offline_pages/prerendering_loader.h
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+// Copyright 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 CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDERING_LOADER_H_
+#define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDERING_LOADER_H_
+
+#include "base/callback.h"
+#include "components/offline_pages/background/offliner.h"
+
+class GURL;
+class PrerenderManager;
+
+namespace content {
+class WebContents;
+class SessionStorageNamespace;
+}  // namespace content
+
+namespace gfx {
+class Size;
+}  // namespace gfx
+
+namespace offline_pages {
+
+// A client-side page loader that integrates with the PrerenderManager to do
+// the page loading in the background.
+class PrerenderingLoader {
+ public:
+  // Reports status of a load page request with loaded contents if available.
+  typedef base::Callback<void(
+      Offliner::CompletionStatus,
+      content::WebContents*)> LoadPageCallback;
+
+  explicit PrerenderingLoader(PrerenderManager* prerender_manager);
+  ~PrerenderingLoader();
+
+  // Loads a page in the background if possible and returns whether the
+  // request was accepted. If so, the LoadPageCallback will be informed
+  // of status. Only one load request may exist as a time. If a previous
+  // request is still in progress it must be canceled before a new
+  // request will be accepted.
+  bool LoadPage(
+      const GURL& url,
+      content::SessionStorageNamespace* session_storage_namespace,
+      const gfx::Size& size,
+      const LoadPageCallback& callback);
+
+  // Stops (completes or cancels) the load request. Must be called when
+  // LoadPageCallback is done with consuming the contents.
+  // This loader should also be responsible for stopping offline
+  // prerenders when Chrome is transitioned to foreground.
+  void StopLoading();
+
+ private:
+  // Not owned.
+  PrerenderManager* prerender_manager_;
+};
+
+}  // namespace offline_pages
+
+#endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDERING_LOADER_H_