Don't insert redundant BR for merging

LayoutTests/editing/deleting/delete-br-001-expected.txt

Index: LayoutTests/editing/deleting/delete-br-001-expected.txt
diff --git a/LayoutTests/editing/deleting/delete-br-001-expected.txt b/LayoutTests/editing/deleting/delete-br-001-expected.txt
index e42555316e16a92be444eee3003910b8d7867c07..630af0b9102b5e43b818e1b5c6f6fdefe6daae38 100644
--- a/LayoutTests/editing/deleting/delete-br-001-expected.txt
+++ b/LayoutTests/editing/deleting/delete-br-001-expected.txt
@@ -1,13 +1,13 @@
 PASS $("work").innerHTML is "abc<br id=\"b\"><br id=\"c\">def"
 PASS selection.type is "Caret"
 PASS selection.anchorOffset is 3
-PASS $("work").innerHTML is "abc<br id=\"a\"><br>def"
+PASS $("work").innerHTML is "abc<br id=\"a\"><br id=\"c\">def"
 PASS selection.type is "Caret"
 PASS selection.anchorOffset is 2
 PASS $("work").innerHTML is "abc<br id=\"a\"><br id=\"b\">def"
 PASS selection.type is "Caret"
 PASS selection.anchorOffset is 0
-PASS $("work").innerHTML is "abc<br>def"
+PASS $("work").innerHTML is "abc<br id=\"c\">def"
 PASS selection.type is "Caret"
 PASS selection.anchorOffset is 3
 PASS $("work").innerHTML is "abc<br id=\"a\">def"