Move and rename RenderBR to LayoutBR.

LayoutTests/platform/mac/fast/forms/button-align-expected.txt

Index: LayoutTests/platform/mac/fast/forms/button-align-expected.txt
diff --git a/LayoutTests/platform/mac/fast/forms/button-align-expected.txt b/LayoutTests/platform/mac/fast/forms/button-align-expected.txt
index 85794600d9770bf395a7cd9a432474f3ee53b48a..05d9782548364c4affeb81d02b82b519fe077b2d 100644
--- a/LayoutTests/platform/mac/fast/forms/button-align-expected.txt
+++ b/LayoutTests/platform/mac/fast/forms/button-align-expected.txt
@@ -13,21 +13,21 @@ layer at (0,0) size 800x600
               text run at (52,0) width 180: "This is should be center justified."
         RenderText {#text} at (300,0) size 4x18
           text run at (300,0) width 4: " "
-        RenderBR {BR} at (0,0) size 0x0
+        LayoutBR {BR} at (0,0) size 0x0
         RenderButton {BUTTON} at (0,20) size 300x18 [bgcolor=#C0C0C0] [border: none (2px outset #C0C0C0) none (2px outset #C0C0C0)]
           RenderBlock (anonymous) at (8,2) size 284x13
             RenderText {#text} at (52,0) size 180x13
               text run at (52,0) width 180: "This is should be center justified."
         RenderText {#text} at (300,19) size 4x18
           text run at (300,19) width 4: " "
-        RenderBR {BR} at (0,0) size 0x0
+        LayoutBR {BR} at (0,0) size 0x0
         RenderButton {BUTTON} at (0,39) size 300x18 [bgcolor=#C0C0C0] [border: none (2px outset #C0C0C0) none (2px outset #C0C0C0)]
           RenderBlock (anonymous) at (8,2) size 284x13
             RenderText {#text} at (52,0) size 180x13
               text run at (52,0) width 180: "This is should be center justified."
         RenderText {#text} at (300,38) size 4x18
           text run at (300,38) width 4: " "
-        RenderBR {BR} at (0,0) size 0x0
+        LayoutBR {BR} at (0,0) size 0x0
         RenderButton {BUTTON} at (0,57) size 300x18 [bgcolor=#C0C0C0] [border: none (2px outset #C0C0C0) none (2px outset #C0C0C0)]
           RenderBlock (anonymous) at (8,2) size 284x13
             RenderText {#text} at (52,0) size 180x13