Move and rename RenderBR to LayoutBR.

LayoutTests/platform/mac/fast/forms/basic-buttons-expected.txt

Index: LayoutTests/platform/mac/fast/forms/basic-buttons-expected.txt
diff --git a/LayoutTests/platform/mac/fast/forms/basic-buttons-expected.txt b/LayoutTests/platform/mac/fast/forms/basic-buttons-expected.txt
index 59a1bb761269b1f3ede812c5e8ee367c7297d416..eafdead35def2549a508bb0245bf74f08da17549 100644
--- a/LayoutTests/platform/mac/fast/forms/basic-buttons-expected.txt
+++ b/LayoutTests/platform/mac/fast/forms/basic-buttons-expected.txt
@@ -6,14 +6,14 @@ layer at (0,0) size 800x294
       RenderBlock (anonymous) at (0,0) size 784x72
         RenderText {#text} at (0,0) size 548x18
           text run at (0,0) width 548: "Tests for basic button rendering. Creates a table with seven columns and seven rows. "
-        RenderBR {BR} at (547,0) size 1x18
+        LayoutBR {BR} at (547,0) size 1x18
         RenderText {#text} at (0,18) size 521x18
           text run at (0,18) width 521: "Creates two different types of buttons, one with an image (a red dot) and another "
-        RenderBR {BR} at (520,18) size 1x18
+        LayoutBR {BR} at (520,18) size 1x18
         RenderText {#text} at (0,36) size 662x18
           text run at (0,36) width 662: "with text (\"foo\") and then uses six different paddings to make sure each of the buttons render properly. "
-        RenderBR {BR} at (661,36) size 1x18
-        RenderBR {BR} at (0,54) size 0x18
+        LayoutBR {BR} at (661,36) size 1x18
+        LayoutBR {BR} at (0,54) size 0x18
       LayoutTable {TABLE} at (0,72) size 697x206
         LayoutTableSection {TBODY} at (0,0) size 697x206
           LayoutTableRow {TR} at (0,0) size 697x20