Move and rename RenderBR to LayoutBR.

LayoutTests/platform/linux/editing/input/reveal-caret-of-multiline-input-expected.txt

 layer at (0,0) size 800x600
   RenderView at (0,0) size 800x600
 layer at (0,0) size 800x207
   RenderBlock {HTML} at (0,0) size 800x207
     RenderBody {BODY} at (8,8) size 784x191
       RenderBlock {DIV} at (0,0) size 784x20
         RenderText {#text} at (0,0) size 568x19
           text run at (0,0) width 568: "When the caret is scrolled out, on starting typing it must be brought to the center of the control."
       RenderBlock (anonymous) at (0,20) size 784x171
         RenderText {#text} at (0,0) size 0x0
         RenderText {#text} at (0,0) size 0x0
 layer at (8,28) size 101x166 clip at (9,29) size 84x164 scrollY 120.00 scrollHeight 516
   LayoutTextControl {TEXTAREA} at (0,0) size 101x166 [bgcolor=#FFFFFF] [border: (1px solid #A9A9A9)]
     RenderBlock {DIV} at (3,3) size 80x512
       RenderText {#text} at (0,0) size 16x16
         text run at (0,0) width 16: "00"
-      RenderBR {BR} at (16,0) size 0x16
+      LayoutBR {BR} at (16,0) size 0x16
       RenderText {#text} at (0,16) size 16x16
         text run at (0,16) width 16: "01"
-      RenderBR {BR} at (16,16) size 0x16
+      LayoutBR {BR} at (16,16) size 0x16
       RenderText {#text} at (0,32) size 16x16
         text run at (0,32) width 16: "02"
-      RenderBR {BR} at (16,32) size 0x16
+      LayoutBR {BR} at (16,32) size 0x16
       RenderText {#text} at (0,48) size 16x16
         text run at (0,48) width 16: "03"
-      RenderBR {BR} at (16,48) size 0x16
+      LayoutBR {BR} at (16,48) size 0x16
       RenderText {#text} at (0,64) size 16x16
         text run at (0,64) width 16: "04"
-      RenderBR {BR} at (16,64) size 0x16
+      LayoutBR {BR} at (16,64) size 0x16
       RenderText {#text} at (0,80) size 16x16
         text run at (0,80) width 16: "05"
-      RenderBR {BR} at (16,80) size 0x16
+      LayoutBR {BR} at (16,80) size 0x16
       RenderText {#text} at (0,96) size 16x16
         text run at (0,96) width 16: "06"
-      RenderBR {BR} at (16,96) size 0x16
+      LayoutBR {BR} at (16,96) size 0x16
       RenderText {#text} at (0,112) size 16x16
         text run at (0,112) width 16: "07"
-      RenderBR {BR} at (16,112) size 0x16
+      LayoutBR {BR} at (16,112) size 0x16
       RenderText {#text} at (0,128) size 16x16
         text run at (0,128) width 16: "08"
-      RenderBR {BR} at (16,128) size 0x16
+      LayoutBR {BR} at (16,128) size 0x16
       RenderText {#text} at (0,144) size 16x16
         text run at (0,144) width 16: "09"
-      RenderBR {BR} at (16,144) size 0x16
+      LayoutBR {BR} at (16,144) size 0x16
       RenderText {#text} at (0,160) size 16x16
         text run at (0,160) width 16: "10"
-      RenderBR {BR} at (16,160) size 0x16
+      LayoutBR {BR} at (16,160) size 0x16
       RenderText {#text} at (0,176) size 16x16
         text run at (0,176) width 16: "11"
-      RenderBR {BR} at (16,176) size 0x16
+      LayoutBR {BR} at (16,176) size 0x16
       RenderText {#text} at (0,192) size 24x16
         text run at (0,192) width 24: ">12"
-      RenderBR {BR} at (24,192) size 0x16
+      LayoutBR {BR} at (24,192) size 0x16
       RenderText {#text} at (0,208) size 16x16
         text run at (0,208) width 16: "13"
-      RenderBR {BR} at (16,208) size 0x16
+      LayoutBR {BR} at (16,208) size 0x16
       RenderText {#text} at (0,224) size 16x16
         text run at (0,224) width 16: "14"
-      RenderBR {BR} at (16,224) size 0x16
+      LayoutBR {BR} at (16,224) size 0x16
       RenderText {#text} at (0,240) size 16x16
         text run at (0,240) width 16: "15"
-      RenderBR {BR} at (16,240) size 0x16
+      LayoutBR {BR} at (16,240) size 0x16
       RenderText {#text} at (0,256) size 16x16
         text run at (0,256) width 16: "16"
-      RenderBR {BR} at (16,256) size 0x16
+      LayoutBR {BR} at (16,256) size 0x16
       RenderText {#text} at (0,272) size 16x16
         text run at (0,272) width 16: "17"
-      RenderBR {BR} at (16,272) size 0x16
+      LayoutBR {BR} at (16,272) size 0x16
       RenderText {#text} at (0,288) size 16x16
         text run at (0,288) width 16: "18"
-      RenderBR {BR} at (16,288) size 0x16
+      LayoutBR {BR} at (16,288) size 0x16
       RenderText {#text} at (0,304) size 16x16
         text run at (0,304) width 16: "19"
-      RenderBR {BR} at (16,304) size 0x16
+      LayoutBR {BR} at (16,304) size 0x16
       RenderText {#text} at (0,320) size 16x16
         text run at (0,320) width 16: "20"
-      RenderBR {BR} at (16,320) size 0x16
+      LayoutBR {BR} at (16,320) size 0x16
       RenderText {#text} at (0,336) size 16x16
         text run at (0,336) width 16: "21"
-      RenderBR {BR} at (16,336) size 0x16
+      LayoutBR {BR} at (16,336) size 0x16
       RenderText {#text} at (0,352) size 16x16
         text run at (0,352) width 16: "22"
-      RenderBR {BR} at (16,352) size 0x16
+      LayoutBR {BR} at (16,352) size 0x16
       RenderText {#text} at (0,368) size 16x16
         text run at (0,368) width 16: "23"
-      RenderBR {BR} at (16,368) size 0x16
+      LayoutBR {BR} at (16,368) size 0x16
       RenderText {#text} at (0,384) size 16x16
         text run at (0,384) width 16: "24"
-      RenderBR {BR} at (16,384) size 0x16
+      LayoutBR {BR} at (16,384) size 0x16
       RenderText {#text} at (0,400) size 16x16
         text run at (0,400) width 16: "25"
-      RenderBR {BR} at (16,400) size 0x16
+      LayoutBR {BR} at (16,400) size 0x16
       RenderText {#text} at (0,416) size 16x16
         text run at (0,416) width 16: "26"
-      RenderBR {BR} at (16,416) size 0x16
+      LayoutBR {BR} at (16,416) size 0x16
       RenderText {#text} at (0,432) size 16x16
         text run at (0,432) width 16: "27"
-      RenderBR {BR} at (16,432) size 0x16
+      LayoutBR {BR} at (16,432) size 0x16
       RenderText {#text} at (0,448) size 16x16
         text run at (0,448) width 16: "28"
-      RenderBR {BR} at (16,448) size 0x16
+      LayoutBR {BR} at (16,448) size 0x16
       RenderText {#text} at (0,464) size 16x16
         text run at (0,464) width 16: "29"
-      RenderBR {BR} at (16,464) size 0x16
+      LayoutBR {BR} at (16,464) size 0x16
       RenderText {#text} at (0,480) size 16x16
         text run at (0,480) width 16: "30"
-      RenderBR {BR} at (16,480) size 0x16
-      RenderBR {BR} at (0,496) size 0x16
+      LayoutBR {BR} at (16,480) size 0x16
+      LayoutBR {BR} at (0,496) size 0x16
 caret: position 1 of child 24 {#text} of child 0 {DIV} of {#document-fragment} of child 3 {TEXTAREA} of body