Move and rename RenderBR to LayoutBR.

LayoutTests/platform/linux/editing/pasteboard/5006779-expected.txt

Index: LayoutTests/platform/linux/editing/pasteboard/5006779-expected.txt
diff --git a/LayoutTests/platform/linux/editing/pasteboard/5006779-expected.txt b/LayoutTests/platform/linux/editing/pasteboard/5006779-expected.txt
index 30ed3a26f971067a97a224ce4b094be7f7c6fcfd..6561d156963deec654255e30bd1f98cfeecc5476 100644
--- a/LayoutTests/platform/linux/editing/pasteboard/5006779-expected.txt
+++ b/LayoutTests/platform/linux/editing/pasteboard/5006779-expected.txt
@@ -11,13 +11,13 @@ layer at (0,0) size 800x600
         RenderBlock (anonymous) at (0,0) size 784x40
           RenderText {#text} at (0,0) size 19x19
             text run at (0,0) width 19: "On"
-          RenderBR {BR} at (19,15) size 0x0
-          RenderBR {BR} at (0,20) size 0x19
+          LayoutBR {BR} at (19,15) size 0x0
+          LayoutBR {BR} at (0,20) size 0x19
         RenderBlock {BLOCKQUOTE} at (0,40) size 784x20 [color=#0000FF] [border: none (2px solid #0000FF)]
           RenderText {#text} at (12,0) size 156x19
             text run at (12,0) width 156: "On Tuesday, Dave wrote:"
         RenderBlock {BLOCKQUOTE} at (0,60) size 784x20 [color=#0000FF] [border: none (2px solid #0000FF)]
-          RenderBR {BR} at (12,0) size 0x19
+          LayoutBR {BR} at (12,0) size 0x19
         RenderBlock {BLOCKQUOTE} at (0,80) size 784x20 [color=#0000FF] [border: none (2px solid #0000FF)]
           RenderText {#text} at (12,0) size 79x19
             text run at (12,0) width 79: "Hello World."