Add Notification images (Blink + desktop implementation)

third_party/WebKit/Source/modules/notifications/Notification.cpp

Index: third_party/WebKit/Source/modules/notifications/Notification.cpp
diff --git a/third_party/WebKit/Source/modules/notifications/Notification.cpp b/third_party/WebKit/Source/modules/notifications/Notification.cpp
index 42da08ac1f503960eb58cc9b1236cadb5efc0e63..470190f8665461cb6f96a9a9a0e089a99d2f911c 100644
--- a/third_party/WebKit/Source/modules/notifications/Notification.cpp
+++ b/third_party/WebKit/Source/modules/notifications/Notification.cpp
@@ -254,6 +254,11 @@ String Notification::tag() const
     return m_data.tag;
 }
 
+String Notification::image() const
+{
+    return m_data.image.string();
+}
+
 String Notification::icon() const
 {
     return m_data.icon.string();