Support for distilling prior pages in an article.

components/dom_distiller/core/distiller.cc

 // 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.
 
 #include "components/dom_distiller/core/distiller.h"
 
 #include <map>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 133 matching lines @@
     current_page->set_url(page_url.spec());
     current_page->set_html(distilled_page->html);
 
     GURL next_page_url(distilled_page->next_page_url);
     if (next_page_url.is_valid()) {
       // The pages should be in same origin.
       DCHECK_EQ(next_page_url.GetOrigin(), page_url.GetOrigin());
       AddToDistillationQueue(page_num + 1, next_page_url);
     }
 
+    GURL prev_page_url(distilled_page->prev_page_url);
+    if (prev_page_url.is_valid()) {
+      DCHECK_EQ(prev_page_url.GetOrigin(), page_url.GetOrigin());
+      AddToDistillationQueue(page_num - 1, prev_page_url);
+    }
+
     for (size_t img_num = 0; img_num < distilled_page->image_urls.size();
          ++img_num) {
       std::string image_id =
           base::IntToString(page_num + 1) + "_" + base::IntToString(img_num);
       FetchImage(page_num, image_id, distilled_page->image_urls[img_num]);
     }
 
     AddPageIfDone(page_num);
     DistillNextPage();
   } else {
@@ skipping 81 matching lines @@
               max_pages_in_article_);
 
     DCHECK(pages_.empty());
     DCHECK(finished_pages_index_.empty());
     distillation_cb_.Run(article_proto.Pass());
     distillation_cb_.Reset();
   }
 }
 
 }  // namespace dom_distiller