Move and rename RenderBR to LayoutBR.

LayoutTests/platform/win-xp/fast/overflow/overflow-stacking-expected.txt

 layer at (0,0) size 800x600 scrollHeight 606
   RenderView at (0,0) size 800x600
 layer at (0,0) size 800x606 backgroundClip at (0,0) size 800x600 clip at (0,0) size 800x600 outlineClip at (0,0) size 800x600
   RenderBlock {HTML} at (0,0) size 800x606
     RenderBody {BODY} at (8,8) size 784x590
       RenderBlock (anonymous) at (0,0) size 784x40
         RenderText {#text} at (0,0) size 782x39
           text run at (0,0) width 782: "Make sure that overflow:auto/hidden/scroll blocks interleave their background and foreground with other overlapping blocks in the"
           text run at (0,20) width 75: "normal flow."
       RenderBlock {DIV} at (0,290) size 300x300 [bgcolor=#FFFF00]
         RenderText {#text} at (0,1) size 171x112
           text run at (0,1) width 166: "This text"
           text run at (0,58) width 171: "overlaps."
 layer at (8,48) size 300x300 clip at (8,48) size 285x300 scrollHeight 940
   RenderBlock {DIV} at (0,40) size 300x300 [bgcolor=#00FF00]
     RenderText {#text} at (0,0) size 71x19
       text run at (0,0) width 71: "Hello world"
-    RenderBR {BR} at (71,15) size 0x0
+    LayoutBR {BR} at (71,15) size 0x0
     RenderText {#text} at (0,20) size 71x19
       text run at (0,20) width 71: "Hello world"
-    RenderBR {BR} at (71,35) size 0x0
+    LayoutBR {BR} at (71,35) size 0x0
     RenderText {#text} at (0,40) size 71x19
       text run at (0,40) width 71: "Hello world"
-    RenderBR {BR} at (71,55) size 0x0
+    LayoutBR {BR} at (71,55) size 0x0
     RenderText {#text} at (0,60) size 71x19
       text run at (0,60) width 71: "Hello world"
-    RenderBR {BR} at (71,75) size 0x0
+    LayoutBR {BR} at (71,75) size 0x0
     RenderText {#text} at (0,80) size 71x19
       text run at (0,80) width 71: "Hello world"
-    RenderBR {BR} at (71,95) size 0x0
+    LayoutBR {BR} at (71,95) size 0x0
     RenderText {#text} at (0,100) size 71x19
       text run at (0,100) width 71: "Hello world"
-    RenderBR {BR} at (71,115) size 0x0
+    LayoutBR {BR} at (71,115) size 0x0
     RenderText {#text} at (0,120) size 71x19
       text run at (0,120) width 71: "Hello world"
-    RenderBR {BR} at (71,135) size 0x0
+    LayoutBR {BR} at (71,135) size 0x0
     RenderText {#text} at (0,140) size 71x19
       text run at (0,140) width 71: "Hello world"
-    RenderBR {BR} at (71,155) size 0x0
+    LayoutBR {BR} at (71,155) size 0x0
     RenderText {#text} at (0,160) size 71x19
       text run at (0,160) width 71: "Hello world"
-    RenderBR {BR} at (71,175) size 0x0
+    LayoutBR {BR} at (71,175) size 0x0
     RenderText {#text} at (0,180) size 71x19
       text run at (0,180) width 71: "Hello world"
-    RenderBR {BR} at (71,195) size 0x0
+    LayoutBR {BR} at (71,195) size 0x0
     RenderText {#text} at (0,200) size 71x19
       text run at (0,200) width 71: "Hello world"
-    RenderBR {BR} at (71,215) size 0x0
+    LayoutBR {BR} at (71,215) size 0x0
     RenderText {#text} at (0,220) size 71x19
       text run at (0,220) width 71: "Hello world"
-    RenderBR {BR} at (71,235) size 0x0
+    LayoutBR {BR} at (71,235) size 0x0
     RenderText {#text} at (0,240) size 71x19
       text run at (0,240) width 71: "Hello world"
-    RenderBR {BR} at (71,255) size 0x0
+    LayoutBR {BR} at (71,255) size 0x0
     RenderText {#text} at (0,260) size 71x19
       text run at (0,260) width 71: "Hello world"
-    RenderBR {BR} at (71,275) size 0x0
+    LayoutBR {BR} at (71,275) size 0x0
     RenderText {#text} at (0,280) size 71x19
       text run at (0,280) width 71: "Hello world"
-    RenderBR {BR} at (71,295) size 0x0
+    LayoutBR {BR} at (71,295) size 0x0
     RenderText {#text} at (0,300) size 71x19
       text run at (0,300) width 71: "Hello world"
-    RenderBR {BR} at (71,315) size 0x0
+    LayoutBR {BR} at (71,315) size 0x0
     RenderText {#text} at (0,320) size 71x19
       text run at (0,320) width 71: "Hello world"
-    RenderBR {BR} at (71,335) size 0x0
+    LayoutBR {BR} at (71,335) size 0x0
     RenderText {#text} at (0,340) size 71x19
       text run at (0,340) width 71: "Hello world"
-    RenderBR {BR} at (71,355) size 0x0
+    LayoutBR {BR} at (71,355) size 0x0
     RenderText {#text} at (0,360) size 71x19
       text run at (0,360) width 71: "Hello world"
-    RenderBR {BR} at (71,375) size 0x0
+    LayoutBR {BR} at (71,375) size 0x0
     RenderText {#text} at (0,380) size 71x19
       text run at (0,380) width 71: "Hello world"
-    RenderBR {BR} at (71,395) size 0x0
+    LayoutBR {BR} at (71,395) size 0x0
     RenderText {#text} at (0,400) size 71x19
       text run at (0,400) width 71: "Hello world"
-    RenderBR {BR} at (71,415) size 0x0
+    LayoutBR {BR} at (71,415) size 0x0
     RenderText {#text} at (0,420) size 71x19
       text run at (0,420) width 71: "Hello world"
-    RenderBR {BR} at (71,435) size 0x0
+    LayoutBR {BR} at (71,435) size 0x0
     RenderText {#text} at (0,440) size 71x19
       text run at (0,440) width 71: "Hello world"
-    RenderBR {BR} at (71,455) size 0x0
+    LayoutBR {BR} at (71,455) size 0x0
     RenderText {#text} at (0,460) size 71x19
       text run at (0,460) width 71: "Hello world"
-    RenderBR {BR} at (71,475) size 0x0
+    LayoutBR {BR} at (71,475) size 0x0
     RenderText {#text} at (0,480) size 71x19
       text run at (0,480) width 71: "Hello world"
-    RenderBR {BR} at (71,495) size 0x0
+    LayoutBR {BR} at (71,495) size 0x0
     RenderText {#text} at (0,500) size 71x19
       text run at (0,500) width 71: "Hello world"
-    RenderBR {BR} at (71,515) size 0x0
+    LayoutBR {BR} at (71,515) size 0x0
     RenderText {#text} at (0,520) size 71x19
       text run at (0,520) width 71: "Hello world"
-    RenderBR {BR} at (71,535) size 0x0
+    LayoutBR {BR} at (71,535) size 0x0
     RenderText {#text} at (0,540) size 71x19
       text run at (0,540) width 71: "Hello world"
-    RenderBR {BR} at (71,555) size 0x0
+    LayoutBR {BR} at (71,555) size 0x0
     RenderText {#text} at (0,560) size 71x19
       text run at (0,560) width 71: "Hello world"
-    RenderBR {BR} at (71,575) size 0x0
+    LayoutBR {BR} at (71,575) size 0x0
     RenderText {#text} at (0,580) size 71x19
       text run at (0,580) width 71: "Hello world"
-    RenderBR {BR} at (71,595) size 0x0
+    LayoutBR {BR} at (71,595) size 0x0
     RenderText {#text} at (0,600) size 71x19
       text run at (0,600) width 71: "Hello world"
-    RenderBR {BR} at (71,615) size 0x0
+    LayoutBR {BR} at (71,615) size 0x0
     RenderText {#text} at (0,620) size 71x19
       text run at (0,620) width 71: "Hello world"
-    RenderBR {BR} at (71,635) size 0x0
+    LayoutBR {BR} at (71,635) size 0x0
     RenderText {#text} at (0,640) size 71x19
       text run at (0,640) width 71: "Hello world"
-    RenderBR {BR} at (71,655) size 0x0
+    LayoutBR {BR} at (71,655) size 0x0
     RenderText {#text} at (0,660) size 71x19
       text run at (0,660) width 71: "Hello world"
-    RenderBR {BR} at (71,675) size 0x0
+    LayoutBR {BR} at (71,675) size 0x0
     RenderText {#text} at (0,680) size 71x19
       text run at (0,680) width 71: "Hello world"
-    RenderBR {BR} at (71,695) size 0x0
+    LayoutBR {BR} at (71,695) size 0x0
     RenderText {#text} at (0,700) size 71x19
       text run at (0,700) width 71: "Hello world"
-    RenderBR {BR} at (71,715) size 0x0
+    LayoutBR {BR} at (71,715) size 0x0
     RenderText {#text} at (0,720) size 71x19
       text run at (0,720) width 71: "Hello world"
-    RenderBR {BR} at (71,735) size 0x0
+    LayoutBR {BR} at (71,735) size 0x0
     RenderText {#text} at (0,740) size 71x19
       text run at (0,740) width 71: "Hello world"
-    RenderBR {BR} at (71,755) size 0x0
+    LayoutBR {BR} at (71,755) size 0x0
     RenderText {#text} at (0,760) size 71x19
       text run at (0,760) width 71: "Hello world"
-    RenderBR {BR} at (71,775) size 0x0
+    LayoutBR {BR} at (71,775) size 0x0
     RenderText {#text} at (0,780) size 71x19
       text run at (0,780) width 71: "Hello world"
-    RenderBR {BR} at (71,795) size 0x0
+    LayoutBR {BR} at (71,795) size 0x0
     RenderText {#text} at (0,800) size 71x19
       text run at (0,800) width 71: "Hello world"
-    RenderBR {BR} at (71,815) size 0x0
+    LayoutBR {BR} at (71,815) size 0x0
     RenderText {#text} at (0,820) size 71x19
       text run at (0,820) width 71: "Hello world"
-    RenderBR {BR} at (71,835) size 0x0
+    LayoutBR {BR} at (71,835) size 0x0
     RenderText {#text} at (0,840) size 71x19
       text run at (0,840) width 71: "Hello world"
-    RenderBR {BR} at (71,855) size 0x0
+    LayoutBR {BR} at (71,855) size 0x0
     RenderText {#text} at (0,860) size 71x19
       text run at (0,860) width 71: "Hello world"
-    RenderBR {BR} at (71,875) size 0x0
+    LayoutBR {BR} at (71,875) size 0x0
     RenderText {#text} at (0,880) size 71x19
       text run at (0,880) width 71: "Hello world"
-    RenderBR {BR} at (71,895) size 0x0
+    LayoutBR {BR} at (71,895) size 0x0
     RenderText {#text} at (0,900) size 71x19
       text run at (0,900) width 71: "Hello world"
-    RenderBR {BR} at (71,915) size 0x0
+    LayoutBR {BR} at (71,915) size 0x0
     RenderText {#text} at (0,920) size 71x19
       text run at (0,920) width 71: "Hello world"
-    RenderBR {BR} at (71,935) size 0x0
+    LayoutBR {BR} at (71,935) size 0x0