Move and rename RenderBR to LayoutBR.

LayoutTests/editing/pasteboard/emacs-cntl-y-001-expected.txt

Index: LayoutTests/editing/pasteboard/emacs-cntl-y-001-expected.txt
diff --git a/LayoutTests/editing/pasteboard/emacs-cntl-y-001-expected.txt b/LayoutTests/editing/pasteboard/emacs-cntl-y-001-expected.txt
index e4e6c472a03a049743a74c159f20527e599d13ab..6ba3928a78892a5fa44c3981c4938fb7cbc29d0b 100644
--- a/LayoutTests/editing/pasteboard/emacs-cntl-y-001-expected.txt
+++ b/LayoutTests/editing/pasteboard/emacs-cntl-y-001-expected.txt
@@ -10,16 +10,16 @@ layer at (0,0) size 800x600
         RenderBlock {DIV} at (14,14) size 756x56
           RenderText {#text} at (0,0) size 67x28
             text run at (0,0) width 67: "Tests: "
-          RenderBR {BR} at (0,0) size 0x0
+          LayoutBR {BR} at (0,0) size 0x0
           RenderText {#text} at (0,28) size 544x28
             text run at (0,28) width 544: "Cntl-y at caret selection when nothing is in the kill ring."
         RenderBlock {DIV} at (14,86) size 756x84
           RenderText {#text} at (0,0) size 189x28
             text run at (0,0) width 189: "Expected Results: "
-          RenderBR {BR} at (189,22) size 0x0
+          LayoutBR {BR} at (189,22) size 0x0
           RenderText {#text} at (0,28) size 291x28
             text run at (0,28) width 291: "Deletes a character, yielding: "
-          RenderBR {BR} at (291,50) size 0x0
+          LayoutBR {BR} at (291,50) size 0x0
           RenderText {#text} at (0,56) size 166x28
             text run at (0,56) width 166: "one tw three four"
       RenderBlock {DIV} at (0,208) size 784x32