[CSSGridLayout] <embed> elements leaving stale pointers into grid

Source/core/rendering/RenderGrid.cpp

Index: Source/core/rendering/RenderGrid.cpp
diff --git a/Source/core/rendering/RenderGrid.cpp b/Source/core/rendering/RenderGrid.cpp
index 2550717785c3938577fe2e03984e08f7e720f2bb..493648c28ae6fd1493c6c8ee750abacb5d87103c 100644
--- a/Source/core/rendering/RenderGrid.cpp
+++ b/Source/core/rendering/RenderGrid.cpp
@@ -206,6 +206,7 @@ void RenderGrid::addChild(RenderObject* newChild, RenderObject* beforeChild)
     if (beforeChild && beforeChild->parent() != this) {
         ASSERT(beforeChild->parent()->isAnonymous());
         beforeChild = splitAnonymousBoxesAroundChild(beforeChild);
+        dirtyGrid();
     }
 
     RenderBlock::addChild(newChild, beforeChild);