Add incremental updates for multipage distillation.

components/dom_distiller/content/dom_distiller_viewer_source.cc

Index: components/dom_distiller/content/dom_distiller_viewer_source.cc
diff --git a/components/dom_distiller/content/dom_distiller_viewer_source.cc b/components/dom_distiller/content/dom_distiller_viewer_source.cc
index 375a542c77aade81760c01823c9f37f4d46cf2fe..53581175d08e31a7fb096902a0ec79432c3ffbf5 100644
--- a/components/dom_distiller/content/dom_distiller_viewer_source.cc
+++ b/components/dom_distiller/content/dom_distiller_viewer_source.cc
@@ -58,6 +58,9 @@ class RequestViewerHandle : public ViewRequestDelegate {
   virtual void OnArticleReady(const DistilledArticleProto* article_proto)
       OVERRIDE;
 
+  virtual void OnArticleUpdated(ArticleDistillationUpdate article_update)
+      OVERRIDE;
+
   void TakeViewerHandle(scoped_ptr<ViewerHandle> viewer_handle);
 
  private:
@@ -101,6 +104,11 @@ void RequestViewerHandle::OnArticleReady(
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }
 
+void RequestViewerHandle::OnArticleUpdated(
+    ArticleDistillationUpdate article_update) {
+  // TODO(nyquist): Add support for displaying pages incrementally.
+}
+
 void RequestViewerHandle::TakeViewerHandle(
     scoped_ptr<ViewerHandle> viewer_handle) {
   viewer_handle_ = viewer_handle.Pass();