<picture>: Update the <img> element when a <source> changes

Source/core/html/HTMLPictureElement.cpp

Index: Source/core/html/HTMLPictureElement.cpp
diff --git a/Source/core/html/HTMLPictureElement.cpp b/Source/core/html/HTMLPictureElement.cpp
index f5a3d95c8c7e9eba160320900a4aabff72adf0f7..ee30bfd1e89549a64b15bfebad3a0a4e3ef17260 100644
--- a/Source/core/html/HTMLPictureElement.cpp
+++ b/Source/core/html/HTMLPictureElement.cpp
@@ -6,6 +6,8 @@
 #include "core/html/HTMLPictureElement.h"
 
 #include "HTMLNames.h"
+#include "core/dom/ElementTraversal.h"
+#include "core/html/HTMLImageElement.h"
 
 namespace WebCore {
 
@@ -17,4 +19,11 @@ HTMLPictureElement::HTMLPictureElement(Document& document)
     ScriptWrappable::init(this);
 }
 
+void HTMLPictureElement::sourceOrMediaChanged()
+{
+    for (HTMLImageElement* imageElement = Traversal<HTMLImageElement>::firstChild(*this); imageElement; imageElement = Traversal<HTMLImageElement>::nextSibling(*imageElement)) {
+        imageElement->selectSourceURL(HTMLImageElement::UpdateNormal);
+    }
+}
+
 } // namespace