Move and rename RenderBR to LayoutBR.

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

Index: LayoutTests/platform/mac/editing/pasteboard/5006779-expected.txt
diff --git a/LayoutTests/platform/mac/editing/pasteboard/5006779-expected.txt b/LayoutTests/platform/mac/editing/pasteboard/5006779-expected.txt
index a715dc9486a096e15e9e5f4fbddc1c0d1e64155a..2505da9b5fa40ad8890bccf6208226148689d234 100644
--- a/LayoutTests/platform/mac/editing/pasteboard/5006779-expected.txt
+++ b/LayoutTests/platform/mac/editing/pasteboard/5006779-expected.txt
@@ -11,13 +11,13 @@ layer at (0,0) size 800x600
         RenderBlock (anonymous) at (0,0) size 784x36
           RenderText {#text} at (0,0) size 20x18
             text run at (0,0) width 20: "On"
-          RenderBR {BR} at (19,14) size 1x0
-          RenderBR {BR} at (0,18) size 0x18
+          LayoutBR {BR} at (19,14) size 1x0
+          LayoutBR {BR} at (0,18) size 0x18
         RenderBlock {BLOCKQUOTE} at (0,36) size 784x18 [color=#0000FF] [border: none (2px solid #0000FF)]
           RenderText {#text} at (12,0) size 165x18
             text run at (12,0) width 165: "On Tuesday, Dave wrote:"
         RenderBlock {BLOCKQUOTE} at (0,54) size 784x18 [color=#0000FF] [border: none (2px solid #0000FF)]
-          RenderBR {BR} at (12,0) size 0x18
+          LayoutBR {BR} at (12,0) size 0x18
         RenderBlock {BLOCKQUOTE} at (0,72) size 784x18 [color=#0000FF] [border: none (2px solid #0000FF)]
           RenderText {#text} at (12,0) size 85x18
             text run at (12,0) width 85: "Hello World."