Reland fix for thumbnail generation.

chrome/browser/thumbnails/thumbnail_tab_helper.h

Index: chrome/browser/thumbnails/thumbnail_tab_helper.h
diff --git a/chrome/browser/thumbnails/thumbnail_tab_helper.h b/chrome/browser/thumbnails/thumbnail_tab_helper.h
index df9a731da1adaf3b3d8b551015a118608715b40b..27af8d8b245081a0bc3054c2e4a5dd5ec9f964d5 100644
--- a/chrome/browser/thumbnails/thumbnail_tab_helper.h
+++ b/chrome/browser/thumbnails/thumbnail_tab_helper.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_THUMBNAILS_THUMBNAIL_TAB_HELPER_H_
 
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "chrome/browser/thumbnails/thumbnailing_context.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -39,7 +40,19 @@ class ThumbnailTabHelper
   void DidStartLoading() override;
   void NavigationStopped() override;
 
-  // Update the thumbnail of the given tab contents if necessary.
+  void DecrementCapturerCount();
+  void UpdateThumbnail(
+      const thumbnails::ThumbnailingContext& context,
+      const SkBitmap& thumbnail);
+  void ProcessCapturedBitmap(
+      scoped_refptr<thumbnails::ThumbnailingAlgorithm> algorithm,
+      const SkBitmap& bitmap,
+      content::ReadbackResponse response);
+
+  void AsyncProcessThumbnail(
+      scoped_refptr<thumbnails::ThumbnailingAlgorithm> algorithm);
+
+// Update the thumbnail of the given tab contents if necessary.
   void UpdateThumbnailIfNecessary(content::WebContents* web_contents);
 
   // Called when a render view host was created for a WebContents.
@@ -49,9 +62,12 @@ class ThumbnailTabHelper
   void WidgetHidden(content::RenderWidgetHost* widget);
 
   content::NotificationRegistrar registrar_;
+  scoped_refptr<thumbnails::ThumbnailingContext> thumbnailing_context_;
 
   bool load_interrupted_;
 
+  base::WeakPtrFactory<ThumbnailTabHelper> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(ThumbnailTabHelper);
 };