Add Notification images (Blink + desktop implementation)

content/public/common/notification_resources.h

Index: content/public/common/notification_resources.h
diff --git a/content/public/common/notification_resources.h b/content/public/common/notification_resources.h
index 2594836eceb0ce2a1bb89a4ab19dc9285adcdf1f..e8c56a539ab6076b070eccb524a81fa5476d3149 100644
--- a/content/public/common/notification_resources.h
+++ b/content/public/common/notification_resources.h
@@ -18,6 +18,10 @@ struct CONTENT_EXPORT NotificationResources {
   NotificationResources(const NotificationResources& other);
   ~NotificationResources();
 
+  // Image for the notification. The bitmap may be empty if the developer did
+  // not provide an image, or fetching of the image failed.
+  SkBitmap image;
+
   // Main icon for the notification. The bitmap may be empty if the developer
   // did not provide an icon, or fetching of the icon failed.
   SkBitmap notification_icon;