Move and rename RenderBR to LayoutBR.

LayoutTests/platform/mac/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 800x174
   RenderBlock {HTML} at (0,0) size 800x174
     RenderBody {BODY} at (8,8) size 784x158
       RenderBlock {DIV} at (0,0) size 784x18
         RenderText {#text} at (0,0) size 610x18
           text run at (0,0) width 610: "When the caret is scrolled out, on starting typing it must be brought to the center of the control."
       RenderBlock (anonymous) at (0,18) size 784x140
         RenderText {#text} at (0,0) size 0x0
         RenderText {#text} at (0,0) size 0x0
 layer at (8,26) size 91x136 clip at (9,27) size 74x134 scrollY 98.00 scrollHeight 420
   LayoutTextControl {TEXTAREA} at (0,0) size 91x136 [bgcolor=#FFFFFF] [border: (1px solid #000000)]
     RenderBlock {DIV} at (3,3) size 70x416
       RenderText {#text} at (0,0) size 14x13
         text run at (0,0) width 14: "00"
-      RenderBR {BR} at (13,0) size 1x13
+      LayoutBR {BR} at (13,0) size 1x13
       RenderText {#text} at (0,13) size 14x13
         text run at (0,13) width 14: "01"
-      RenderBR {BR} at (13,13) size 1x13
+      LayoutBR {BR} at (13,13) size 1x13
       RenderText {#text} at (0,26) size 14x13
         text run at (0,26) width 14: "02"
-      RenderBR {BR} at (13,26) size 1x13
+      LayoutBR {BR} at (13,26) size 1x13
       RenderText {#text} at (0,39) size 14x13
         text run at (0,39) width 14: "03"
-      RenderBR {BR} at (13,39) size 1x13
+      LayoutBR {BR} at (13,39) size 1x13
       RenderText {#text} at (0,52) size 14x13
         text run at (0,52) width 14: "04"
-      RenderBR {BR} at (13,52) size 1x13
+      LayoutBR {BR} at (13,52) size 1x13
       RenderText {#text} at (0,65) size 14x13
         text run at (0,65) width 14: "05"
-      RenderBR {BR} at (13,65) size 1x13
+      LayoutBR {BR} at (13,65) size 1x13
       RenderText {#text} at (0,78) size 14x13
         text run at (0,78) width 14: "06"
-      RenderBR {BR} at (13,78) size 1x13
+      LayoutBR {BR} at (13,78) size 1x13
       RenderText {#text} at (0,91) size 14x13
         text run at (0,91) width 14: "07"
-      RenderBR {BR} at (13,91) size 1x13
+      LayoutBR {BR} at (13,91) size 1x13
       RenderText {#text} at (0,104) size 14x13
         text run at (0,104) width 14: "08"
-      RenderBR {BR} at (13,104) size 1x13
+      LayoutBR {BR} at (13,104) size 1x13
       RenderText {#text} at (0,117) size 14x13
         text run at (0,117) width 14: "09"
-      RenderBR {BR} at (13,117) size 1x13
+      LayoutBR {BR} at (13,117) size 1x13
       RenderText {#text} at (0,130) size 14x13
         text run at (0,130) width 14: "10"
-      RenderBR {BR} at (13,130) size 1x13
+      LayoutBR {BR} at (13,130) size 1x13
       RenderText {#text} at (0,143) size 14x13
         text run at (0,143) width 14: "11"
-      RenderBR {BR} at (13,143) size 1x13
+      LayoutBR {BR} at (13,143) size 1x13
       RenderText {#text} at (0,156) size 23x13
         text run at (0,156) width 23: ">12"
-      RenderBR {BR} at (22,156) size 1x13
+      LayoutBR {BR} at (22,156) size 1x13
       RenderText {#text} at (0,169) size 14x13
         text run at (0,169) width 14: "13"
-      RenderBR {BR} at (13,169) size 1x13
+      LayoutBR {BR} at (13,169) size 1x13
       RenderText {#text} at (0,182) size 14x13
         text run at (0,182) width 14: "14"
-      RenderBR {BR} at (13,182) size 1x13
+      LayoutBR {BR} at (13,182) size 1x13
       RenderText {#text} at (0,195) size 14x13
         text run at (0,195) width 14: "15"
-      RenderBR {BR} at (13,195) size 1x13
+      LayoutBR {BR} at (13,195) size 1x13
       RenderText {#text} at (0,208) size 14x13
         text run at (0,208) width 14: "16"
-      RenderBR {BR} at (13,208) size 1x13
+      LayoutBR {BR} at (13,208) size 1x13
       RenderText {#text} at (0,221) size 14x13
         text run at (0,221) width 14: "17"
-      RenderBR {BR} at (13,221) size 1x13
+      LayoutBR {BR} at (13,221) size 1x13
       RenderText {#text} at (0,234) size 14x13
         text run at (0,234) width 14: "18"
-      RenderBR {BR} at (13,234) size 1x13
+      LayoutBR {BR} at (13,234) size 1x13
       RenderText {#text} at (0,247) size 14x13
         text run at (0,247) width 14: "19"
-      RenderBR {BR} at (13,247) size 1x13
+      LayoutBR {BR} at (13,247) size 1x13
       RenderText {#text} at (0,260) size 14x13
         text run at (0,260) width 14: "20"
-      RenderBR {BR} at (13,260) size 1x13
+      LayoutBR {BR} at (13,260) size 1x13
       RenderText {#text} at (0,273) size 14x13
         text run at (0,273) width 14: "21"
-      RenderBR {BR} at (13,273) size 1x13
+      LayoutBR {BR} at (13,273) size 1x13
       RenderText {#text} at (0,286) size 14x13
         text run at (0,286) width 14: "22"
-      RenderBR {BR} at (13,286) size 1x13
+      LayoutBR {BR} at (13,286) size 1x13
       RenderText {#text} at (0,299) size 14x13
         text run at (0,299) width 14: "23"
-      RenderBR {BR} at (13,299) size 1x13
+      LayoutBR {BR} at (13,299) size 1x13
       RenderText {#text} at (0,312) size 14x13
         text run at (0,312) width 14: "24"
-      RenderBR {BR} at (13,312) size 1x13
+      LayoutBR {BR} at (13,312) size 1x13
       RenderText {#text} at (0,325) size 14x13
         text run at (0,325) width 14: "25"
-      RenderBR {BR} at (13,325) size 1x13
+      LayoutBR {BR} at (13,325) size 1x13
       RenderText {#text} at (0,338) size 14x13
         text run at (0,338) width 14: "26"
-      RenderBR {BR} at (13,338) size 1x13
+      LayoutBR {BR} at (13,338) size 1x13
       RenderText {#text} at (0,351) size 14x13
         text run at (0,351) width 14: "27"
-      RenderBR {BR} at (13,351) size 1x13
+      LayoutBR {BR} at (13,351) size 1x13
       RenderText {#text} at (0,364) size 14x13
         text run at (0,364) width 14: "28"
-      RenderBR {BR} at (13,364) size 1x13
+      LayoutBR {BR} at (13,364) size 1x13
       RenderText {#text} at (0,377) size 14x13
         text run at (0,377) width 14: "29"
-      RenderBR {BR} at (13,377) size 1x13
+      LayoutBR {BR} at (13,377) size 1x13
       RenderText {#text} at (0,390) size 14x13
         text run at (0,390) width 14: "30"
-      RenderBR {BR} at (13,390) size 1x13
-      RenderBR {BR} at (0,403) size 0x13
+      LayoutBR {BR} at (13,390) size 1x13
+      LayoutBR {BR} at (0,403) size 0x13
 caret: position 1 of child 24 {#text} of child 0 {DIV} of {#document-fragment} of child 3 {TEXTAREA} of body