Make Event.path() return a pre-calculated NodeList rather than calculating it dynamically.

LayoutTests/fast/dom/shadow/event-path-with-dom-mutation-expected.txt

Index: LayoutTests/fast/dom/shadow/event-path-with-dom-mutation-expected.txt
diff --git a/LayoutTests/fast/dom/shadow/event-path-in-shadow-tree-expected.txt b/LayoutTests/fast/dom/shadow/event-path-with-dom-mutation-expected.txt
similarity index 98%
copy from LayoutTests/fast/dom/shadow/event-path-in-shadow-tree-expected.txt
copy to LayoutTests/fast/dom/shadow/event-path-with-dom-mutation-expected.txt
index 46ac28967b0deee950019ceebba1dc477669a416..2d70a1132a0c82f218c32ae80b96915e1e568b09 100644
--- a/LayoutTests/fast/dom/shadow/event-path-in-shadow-tree-expected.txt
+++ b/LayoutTests/fast/dom/shadow/event-path-with-dom-mutation-expected.txt
@@ -5,6 +5,8 @@ event.path() on node #C
 event.path() on node #B
 #C, #B, #A, #sandbox, [object HTMLBodyElement], [object HTMLHtmlElement], [object HTMLDocument], length: 7
 
+Removing node #C
+
 event.path() on node #F
 #C, #B, #F, #E, #D, #A, #sandbox, [object HTMLBodyElement], [object HTMLHtmlElement], [object HTMLDocument], length: 10
 
@@ -14,6 +16,8 @@ event.path() on node #J
 event.path() on node #I
 #C, #B, #F, #J, #I, #H, #G, #E, #D, #A, #sandbox, [object HTMLBodyElement], [object HTMLHtmlElement], [object HTMLDocument], length: 14
 
+Removing node #J
+
 event.path() on node #M
 #C, #B, #F, #J, #I, #M, #L, #K, #H, #G, #E, #D, #A, #sandbox, [object HTMLBodyElement], [object HTMLHtmlElement], [object HTMLDocument], length: 17