canMergeLists() should make sure that the list items do not belong to the same list

Source/core/editing/htmlediting.cpp

Index: Source/core/editing/htmlediting.cpp
diff --git a/Source/core/editing/htmlediting.cpp b/Source/core/editing/htmlediting.cpp
index 3ab1c75b6a68424f3762bc8d7c392cdb789cd1e2..5cf97d16de6444cd6006bd55b74c7585f992a7b0 100644
--- a/Source/core/editing/htmlediting.cpp
+++ b/Source/core/editing/htmlediting.cpp
@@ -714,7 +714,7 @@ HTMLElement* outermostEnclosingList(Node* node, Node* rootList)
 
 bool canMergeLists(Element* firstList, Element* secondList)
 {
-    if (!firstList || !secondList || !firstList->isHTMLElement() || !secondList->isHTMLElement())
+    if (!firstList || !secondList || firstList == secondList || !firstList->isHTMLElement() || !secondList->isHTMLElement())

[yosin_UTC9, 2014/04/22 04:42:52]

I think caller should not pass same |Element| to |firstList| and |secondList|.
This case should be in assert rather than if-statement.

         return false;
 
     return firstList->hasTagName(secondList->tagQName()) // make sure the list types match (ol vs. ul)