Move and rename RenderBR to LayoutBR.

LayoutTests/platform/win-xp/tables/mozilla/bugs/bug8858-expected.txt

 layer at (0,0) size 800x600 scrollHeight 601
   RenderView at (0,0) size 800x600
 layer at (0,0) size 800x601 backgroundClip at (0,0) size 800x600 clip at (0,0) size 800x600 outlineClip at (0,0) size 800x600
   RenderBlock {HTML} at (0,0) size 800x601
     RenderBody {BODY} at (8,8) size 784x585
       RenderBlock {P} at (0,0) size 784x40
         RenderText {#text} at (0,0) size 477x19
           text run at (0,0) width 405: "there's a table below this line with cellspacing=1 and border=2 and "
           text run at (405,0) width 72: "several lines"
-        RenderBR {BR} at (477,15) size 0x0
+        LayoutBR {BR} at (477,15) size 0x0
         RenderText {#text} at (0,20) size 393x19
           text run at (0,20) width 393: "of content beginning 'Pacific Shore Properties ...'. Can you see it?"
       LayoutTable {TABLE} at (0,56) size 776x529 [border: (2px outset #808080)]
         LayoutTableSection {TBODY} at (2,2) size 772x525
           LayoutTableRow {TR} at (0,1) size 772x129
             LayoutTableCell {TD} at (1,1) size 770x214 [bgcolor=#FFFFFF] [border: (1px inset #808080)] [r=0 c=0 rs=4 cs=2]
               RenderBlock {P} at (5,5) size 760x44
                 RenderInline {FONT} at (0,0) size 23x27 [color=#E91C05]
                   RenderText {#text} at (0,0) size 23x27
                     text run at (0,0) width 23: "W"
                 RenderInline {B} at (0,0) size 228x19
                   RenderInline {FONT} at (0,0) size 228x19 [color=#E91C05]
                     RenderText {#text} at (23,6) size 228x19
                       text run at (23,6) width 228: "elcome to Pacific Shore Properties"
-                    RenderBR {BR} at (251,21) size 0x0
+                    LayoutBR {BR} at (251,21) size 0x0
                 RenderInline {FONT} at (0,0) size 359x16
                   RenderText {#text} at (0,28) size 359x16
                     text run at (0,28) width 359: "Pacific Shore Properties is situated on beautiful Mayne Island."
               RenderBlock {P} at (5,65) size 760x48
                 RenderInline {FONT} at (0,0) size 731x48
                   RenderText {#text} at (0,0) size 731x32
                     text run at (0,0) width 731: "Mayne Island is one of the southern Gulf Islands, off the coast of British Columbia, Canada, between Vancouver and Vancouver"
                     text run at (0,16) width 38: "Island."
-                  RenderBR {BR} at (38,29) size 0x0
+                  LayoutBR {BR} at (38,29) size 0x0
                   RenderText {#text} at (0,32) size 85x16
                     text run at (0,32) width 85: "(See map: left)"
               RenderBlock {P} at (5,129) size 760x80
                 RenderInline {FONT} at (0,0) size 743x80
                   RenderText {#text} at (0,0) size 743x32
                     text run at (0,0) width 743: "Pacific Shore Properties specializes in the diverse properties of the Southern Gulf Islands; which include Beach, Business, View,"
                     text run at (0,16) width 256: "Acreage, Home, Retirement and Recreation."
-                  RenderBR {BR} at (256,29) size 0x0
-                  RenderBR {BR} at (0,32) size 0x16
+                  LayoutBR {BR} at (256,29) size 0x0
+                  LayoutBR {BR} at (0,32) size 0x16
                   RenderText {#text} at (0,48) size 714x32
                     text run at (0,48) width 714: "In business for over 35 years, and the oldest real estate company on Mayne Island, Pacific Shore Properties knowledge and"
                     text run at (0,64) width 251: "expertise on the Gulf Islands is unmatched."
               RenderBlock {P} at (5,225) size 760x0
           LayoutTableRow {TR} at (0,131) size 772x130
           LayoutTableRow {TR} at (0,262) size 772x130
           LayoutTableRow {TR} at (0,393) size 772x131