Improve syncing between dom distiller and the print preview request

components/dom_distiller/core/dom_distiller_service.h

 // Copyright 2013 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_DOM_DISTILLER_CORE_DOM_DISTILLER_SERVICE_H_
 #define COMPONENTS_DOM_DISTILLER_CORE_DOM_DISTILLER_SERVICE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 74 matching lines @@
 
   // Request to view an article by url.
   // Use CreateDefaultDistillerPage() to create a default |distiller_page|.
   // The provided |distiller_page| is only used if there is not already a
   // distillation task in progress for the given |url|.
   virtual scoped_ptr<ViewerHandle> ViewUrl(
       ViewRequestDelegate* delegate,
       scoped_ptr<DistillerPage> distiller_page,
       const GURL& url) = 0;
 
+  // Adds |delegate| to the provided |url| task tracker.
+  // If the given |url| has no task tracker (i.e. has no current
+  // distillation request underway), this will return nullptr - therefore
+  // this should only be called after previously requesting a distillation.
+
+  // If the inclusion of |delegate| on the |url| task tracker was
+  // successful, returns a |ViewerHandle| from the task tracker. This
+  // |ViewerHandle| can be held by client code as long as it wants to
+  // receive callbacks as a |ViewRequestDelegate|.
+
+  // Upon successful inclusion (i.e. a |ViewerHandle| was returned),
+  // the following holds:
+  //
+  // 1) client code will get all future OnArticleUpdated() callbacks for
+  // as long as the distillation process is running.
+  //
+  // 2) client code will get at least the OnArticleFinished()
+  // callback, considering:
+  // 2.a) If the article distillation is not finished yet, the
+  // callback will trigger at the same time as when the original
+  // distillation request gets it.
+  // 2.b) Client code will immediately get this callback after adding
+  // the viewer. If the original distillation request has already
+  // gotten this callback, it has also previously posted it
+  // to a valid standing task tracker.
+
+  // If the inclusion was not successful (i.e. this function
+  // returned nullptr), client code will not get any callbacks.
+  virtual scoped_ptr<ViewerHandle> AddViewRequestDelegate(
+      ViewRequestDelegate* delegate,
+      const GURL& url) = 0;
+
   // Creates a default DistillerPage.
   virtual scoped_ptr<DistillerPage> CreateDefaultDistillerPage(
       const gfx::Size& render_view_size) = 0;
   virtual scoped_ptr<DistillerPage> CreateDefaultDistillerPageWithHandle(
       scoped_ptr<SourcePageHandle> handle) = 0;
 
   virtual void AddObserver(DomDistillerObserver* observer) = 0;
   virtual void RemoveObserver(DomDistillerObserver* observer) = 0;
 
   // Returns the DistilledPagePrefs owned by the instance of
@@ skipping 25 matching lines @@
   bool HasEntry(const std::string& entry_id) override;
   std::string GetUrlForEntry(const std::string& entry_id) override;
   std::vector<ArticleEntry> GetEntries() const override;
   scoped_ptr<ArticleEntry> RemoveEntry(const std::string& entry_id) override;
   scoped_ptr<ViewerHandle> ViewEntry(ViewRequestDelegate* delegate,
                                      scoped_ptr<DistillerPage> distiller_page,
                                      const std::string& entry_id) override;
   scoped_ptr<ViewerHandle> ViewUrl(ViewRequestDelegate* delegate,
                                    scoped_ptr<DistillerPage> distiller_page,
                                    const GURL& url) override;
+  scoped_ptr<ViewerHandle> AddViewRequestDelegate(ViewRequestDelegate* delegate,
+                                                  const GURL& url) override;
   scoped_ptr<DistillerPage> CreateDefaultDistillerPage(
       const gfx::Size& render_view_size) override;
   scoped_ptr<DistillerPage> CreateDefaultDistillerPageWithHandle(
       scoped_ptr<SourcePageHandle> handle) override;
   void AddObserver(DomDistillerObserver* observer) override;
   void RemoveObserver(DomDistillerObserver* observer) override;
   DistilledPagePrefs* GetDistilledPagePrefs() override;
 
  private:
   void CancelTask(TaskTracker* task);
@@ skipping 24 matching lines @@
 
   typedef ScopedVector<TaskTracker> TaskList;
   TaskList tasks_;
 
   DISALLOW_COPY_AND_ASSIGN(DomDistillerService);
 };
 
 }  // namespace dom_distiller
 
 #endif  // COMPONENTS_DOM_DISTILLER_CORE_DOM_DISTILLER_SERVICE_H_