Bug 1383641 - GetFlatTextLengthInRange shouldn't use nsIDOMNode version of nsRange::SetStart. r=masayuki

nsGenericDOMDataNode::SetData uses GetFlatTextLengthInRange.  But GetFlatTextLengthInRange still use nsIDOMNode.  It means that we need additional QI twice.  So we should use nsINode version directly instead.

MozReview-Commit-ID: 3FX0uPGh53O

--HG--
extra : rebase_source : 1a4689ae8744062af8cc1f112b89075ddf3e1271

dom/events/ContentEventHandler.h

@@ -166,18 +166,30 @@ public:
     }
     nsresult SetToRangeStart(nsRange* aRange) const
     {
-      nsCOMPtr<nsIDOMNode> domNode(do_QueryInterface(mNode));
-      return aRange->SetStart(domNode, mOffset);
+      if (!IsValid()) {
+        return NS_ERROR_FAILURE;
+      }
+      ErrorResult errorResult;
+      aRange->SetStart(*mNode, mOffset, errorResult);
+      return errorResult.StealNSResult();
     }
     nsresult SetToRangeEnd(nsRange* aRange) const
     {
-      nsCOMPtr<nsIDOMNode> domNode(do_QueryInterface(mNode));
-      return aRange->SetEnd(domNode, mOffset);
+      if (!IsValid()) {
+        return NS_ERROR_FAILURE;
+      }
+      ErrorResult errorResult;
+      aRange->SetEnd(*mNode, mOffset, errorResult);
+      return errorResult.StealNSResult();
     }
     nsresult SetToRangeEndAfter(nsRange* aRange) const
     {
-      nsCOMPtr<nsIDOMNode> domNode(do_QueryInterface(mNode));
-      return aRange->SetEndAfter(domNode);
+      if (!IsValid()) {
+        return NS_ERROR_FAILURE;
+      }
+      ErrorResult errorResult;
+      aRange->SetEndAfter(*mNode, errorResult);
+      return errorResult.StealNSResult();
     }
   };