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..5723bb2d86e6bb6315e285faed179207562ca2e9 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"
@@ -39,8 +40,26 @@ class ThumbnailTabHelper
   void DidStartLoading() override;
   void NavigationStopped() override;
 
+  // Clean up after thumbnail generation has ended.

[Lei Zhang, 2016/01/12 01:54:46]

Might be good to put this list in chronological order, since these are declared
here. Whereas before, they were in reverse order in the anonymous namespace to
avoid the need to forward declare. The ordering in the .cpp should be flipped as
well.

UpdateThumbnailIfNecessary()
AsyncProcessThumbnail()
ProcessCapturedBitmap()
UpdateThumbnail()
CleanUpFromThumbnailGeneration()

[shrike, 2016/01/12 19:52:39]

OK.

+  void CleanUpFromThumbnailGeneration();
+
+  // Pass the thumbnail to the thumbnail service.
+  void UpdateThumbnail(
+      const thumbnails::ThumbnailingContext& context,
+      const SkBitmap& thumbnail);
+
+  // Create a thumbnail from the web contents bitmap.
+  void ProcessCapturedBitmap(
+      scoped_refptr<thumbnails::ThumbnailingAlgorithm> algorithm,
+      const SkBitmap& bitmap,
+      content::ReadbackResponse response);
+
+  // Initiate asynchronous generation of a thumbnail from the web contents.
+  void AsyncProcessThumbnail(
+      scoped_refptr<thumbnails::ThumbnailService> thumbnail_service);
+
   // Update the thumbnail of the given tab contents if necessary.
-  void UpdateThumbnailIfNecessary(content::WebContents* web_contents);
+  void UpdateThumbnailIfNecessary();
 
   // Called when a render view host was created for a WebContents.
   void RenderViewHostCreated(content::RenderViewHost* renderer);
@@ -49,9 +68,12 @@ 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);
 };