PrerenderingLoader initial integration with PrerenderManager/PrerenderHandle and make it unit-testa…

chrome/browser/android/offline_pages/prerender_adapter.h

+// 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_PRERENDER_ADAPTER_H_
+#define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDER_ADAPTER_H_
+
+#include <memory>
+
+#include "chrome/browser/prerender/prerender_handle.h"
+
+class GURL;
+
+namespace content {
+class BrowserContext;
+class WebContents;
+class SessionStorageNamespace;
+}  // namespace content
+
+namespace gfx {
+class Size;
+}  // namespace gfx
+
+namespace offline_pages {
+
+// An adapter for managing a prerendering request for offlining. This handles
+// all calls into the prerender stack and tracks the active prerender handle.
+class PrerenderAdapter : public prerender::PrerenderHandle::Observer {
+ public:
+  // An observer of PrerenderHandle events that does not expose the handle.
+  class Observer {
+   public:
+    // Signals that the prerender has started running.
+    virtual void OnPrerenderStart() = 0;
+
+    // Signals that the prerender has had its load event.
+    virtual void OnPrerenderStopLoading() = 0;
+
+    // Signals that the prerender has had its 'DOMContentLoaded' event.
+    virtual void OnPrerenderDomContentLoaded() = 0;
+
+    // Signals that the prerender has stopped running and any retrieved
+    // WebContents (via |GetWebContents()|) have become invalidated.
+    virtual void OnPrerenderStop() = 0;
+
+   protected:
+    Observer();
+    virtual ~Observer();
+  };
+
+  explicit PrerenderAdapter(PrerenderAdapter::Observer* observer);
+  ~PrerenderAdapter() override;
+
+  // Returns whether prerendering is enabled and configured.
+  virtual bool CanPrerender() const;
+
+  // Starts prerendering |url| for offlining. There must be no active
+  // prerender request when calling this. Returns whether it was able
+  // to start the prerendering operation.
+  virtual bool StartPrerender(
+      content::BrowserContext* browser_context,
+      const GURL& url,
+      content::SessionStorageNamespace* session_storage_namespace,
+      const gfx::Size& size);
+
+  // Returns a pointer to the prerendered WebContents. This should only be
+  // called once prerendering observer events indicate content is loaded.
+  // It may be used for snapshotting the page. The caller does NOT get
+  // ownership on the contents and must call |DestroyActive()|
+  // to report when it no longer needs the web contents. The caller should
+  // watch for its |PrerenderAdapter::Observer::OnPrerenderStop()| to
+  // learn that the web contents should no longer be used.
+  virtual content::WebContents* GetWebContents() const;
+
+  // Returns the final status of prerendering.
+  virtual prerender::FinalStatus GetFinalStatus() const;
+
+  // Returns whether this adapter has an active prerender request. This
+  // adapter supports one request at a time. DestroyActive() may be used
+  // to clear an active request (which will allow StartPrerender() to be
+  // called to request a new one).
+  virtual bool IsActive() const;
+
+  // Cancels any current prerendering operation and destroys its local handle.
+  virtual void DestroyActive();
+
+  // PrerenderHandle::Observer interface:
+  void OnPrerenderStart(prerender::PrerenderHandle* handle) override;
+  void OnPrerenderStopLoading(prerender::PrerenderHandle* handle) override;
+  void OnPrerenderDomContentLoaded(prerender::PrerenderHandle* handle) override;
+  void OnPrerenderStop(prerender::PrerenderHandle* handle) override;
+
+ private:
+  // At most one prerender request may be active for this adapter and this
+  // holds its handle if one is active.
+  std::unique_ptr<prerender::PrerenderHandle> active_handle_;
+
+  // Observer of active handle events. Not owned.
+  PrerenderAdapter::Observer* observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrerenderAdapter);
+};
+
+}  // namespace offline_pages
+
+#endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PRERENDER_ADAPTER_H_