Improve syncing between dom distiller and the print preview request

chrome/browser/ui/webui/print_preview/print_preview_distiller.cc

Index: chrome/browser/ui/webui/print_preview/print_preview_distiller.cc
diff --git a/chrome/browser/ui/webui/print_preview/print_preview_distiller.cc b/chrome/browser/ui/webui/print_preview/print_preview_distiller.cc
index f3076d92fcdc5cc124ac5afff6cd3a56280d1502..9472bc3ab9a18c8eaec2c7fba3ebbdd1e51c1b37 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_distiller.cc
+++ b/chrome/browser/ui/webui/print_preview/print_preview_distiller.cc
@@ -12,6 +12,7 @@
 #include "base/feature_list.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/chrome_notification_types.h"
+#include "chrome/browser/dom_distiller/dom_distiller_service_factory.h"
 #include "chrome/browser/dom_distiller/tab_utils.h"
 #include "chrome/browser/printing/print_preview_dialog_controller.h"
 #include "chrome/browser/printing/print_preview_message_handler.h"
@@ -20,6 +21,8 @@
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/prerender_messages.h"
 #include "components/dom_distiller/content/browser/distiller_javascript_utils.h"
+#include "components/dom_distiller/core/dom_distiller_service.h"
+#include "components/dom_distiller/core/task_tracker.h"
 #include "components/printing/common/print_messages.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_frame_host.h"
@@ -36,18 +39,23 @@ using content::OpenURLParams;
 using content::RenderViewHost;
 using content::SessionStorageNamespace;
 using content::WebContents;
+using dom_distiller::DomDistillerService;
+using dom_distiller::DomDistillerServiceFactory;
 
 class PrintPreviewDistiller::WebContentsDelegateImpl
     : public content::WebContentsDelegate,
       public content::NotificationObserver,
-      public content::WebContentsObserver {
+      public content::WebContentsObserver,
+      public dom_distiller::ViewRequestDelegate {
  public:
   explicit WebContentsDelegateImpl(WebContents* web_contents,
                                    scoped_ptr<base::DictionaryValue> settings,
                                    const base::Closure on_failed_callback)
       : content::WebContentsObserver(web_contents),
         settings_(std::move(settings)),
-        on_failed_callback_(on_failed_callback) {
+        on_failed_callback_(on_failed_callback),
+        distilled_article_ready_(false),
+        initial_content_loaded_(false) {
     web_contents->SetDelegate(this);
 
     // Close ourselves when the application is shutting down.
@@ -141,6 +149,17 @@ class PrintPreviewDistiller::WebContentsDelegateImpl
     dom_distiller::RunIsolatedJavaScript(
         web_contents()->GetMainFrame(),
         "navigate_on_initial_content_load = true;");
+    initial_content_loaded_ = true;
+  }
+
+  void MaybePrintPreview() {
+    // Wait until we are done distilling the article and the target
+    // WebContents is ready for printing.
+    if (distilled_article_ready_ && initial_content_loaded_) {

[Bernhard Bauer, 2016/01/19 17:21:02]

You could return early if this condition is false.

[mvendramini_hp, 2016/01/20 11:56:57]

Done.

+      RenderViewHost* rvh = web_contents()->GetRenderViewHost();
+      rvh->Send(new PrintMsg_InitiatePrintPreview(rvh->GetRoutingID(), false));
+      rvh->Send(new PrintMsg_PrintPreview(rvh->GetRoutingID(), *settings_));
+    }
   }
 
   void DidNavigateMainFrame(
@@ -149,9 +168,7 @@ class PrintPreviewDistiller::WebContentsDelegateImpl
     // The second content loads signals that the distilled contents have
     // been delivered to the page via inline JavaScript execution.
     if (web_contents()->GetController().GetEntryCount() > 1) {
-      RenderViewHost* rvh = web_contents()->GetRenderViewHost();
-      rvh->Send(new PrintMsg_InitiatePrintPreview(rvh->GetRoutingID(), false));
-      rvh->Send(new PrintMsg_PrintPreview(rvh->GetRoutingID(), *settings_));
+      MaybePrintPreview();
     }
   }
 
@@ -201,12 +218,24 @@ class PrintPreviewDistiller::WebContentsDelegateImpl
     }
   }
 
+  void OnArticleReady(
+      const dom_distiller::DistilledArticleProto* article_proto) override {
+    distilled_article_ready_ = true;
+    MaybePrintPreview();
+  }
+
+  void OnArticleUpdated(
+      dom_distiller::ArticleDistillationUpdate article_update) override {}
+
  private:
   scoped_ptr<base::DictionaryValue> settings_;
   content::NotificationRegistrar notification_registrar_;
 
   // The callback called when the preview failed.
   base::Closure on_failed_callback_;
+
+  bool distilled_article_ready_;
+  bool initial_content_loaded_;
 };
 
 const base::Feature PrintPreviewDistiller::kFeature = {
@@ -228,6 +257,15 @@ PrintPreviewDistiller::PrintPreviewDistiller(
 
   DCHECK(web_contents_);
   ::DistillAndView(source_web_contents, web_contents_.get());
+
+  DomDistillerService* dom_distiller_service =
+      DomDistillerServiceFactory::GetForBrowserContext(
+          source_web_contents->GetBrowserContext());
+
+  const GURL& url = source_web_contents->GetLastCommittedURL();
+
+  viewer_handle_ = dom_distiller_service->AddViewRequestDelegate(
+      web_contents_delegate_.get(), url);
 }
 
 void PrintPreviewDistiller::CreateDestinationWebContents(