Move and rename RenderBR to LayoutBR.

LayoutTests/platform/mac/tables/mozilla/bugs/bug8858-expected.txt

 layer at (0,0) size 800x600
   RenderView at (0,0) size 800x600
 layer at (0,0) size 800x600
   RenderBlock {HTML} at (0,0) size 800x600
     RenderBody {BODY} at (8,8) size 784x584
       RenderBlock {P} at (0,0) size 784x36
         RenderText {#text} at (0,0) size 512x18
           text run at (0,0) width 432: "there's a table below this line with cellspacing=1 and border=2 and "
           text run at (431,0) width 81: "several lines"
-        RenderBR {BR} at (511,14) size 1x0
+        LayoutBR {BR} at (511,14) size 1x0
         RenderText {#text} at (0,18) size 419x18
           text run at (0,18) width 419: "of content beginning 'Pacific Shore Properties ...'. Can you see it?"
       LayoutTable {TABLE} at (0,52) 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 770x205 [bgcolor=#FFFFFF] [border: (1px inset #808080)] [r=0 c=0 rs=4 cs=2]
               RenderBlock {P} at (5,5) size 760x43
                 RenderInline {FONT} at (0,0) size 23x28 [color=#E91C05]
                   RenderText {#text} at (0,0) size 23x28
                     text run at (0,0) width 23: "W"
                 RenderInline {B} at (0,0) size 235x18
                   RenderInline {FONT} at (0,0) size 235x18 [color=#E91C05]
                     RenderText {#text} at (22,8) size 235x18
                       text run at (22,8) width 235: "elcome to Pacific Shore Properties"
-                    RenderBR {BR} at (256,22) size 1x0
+                    LayoutBR {BR} at (256,22) size 1x0
                 RenderInline {FONT} at (0,0) size 357x15
                   RenderText {#text} at (0,28) size 357x15
                     text run at (0,28) width 357: "Pacific Shore Properties is situated on beautiful Mayne Island."
               RenderBlock {P} at (5,64) size 760x45
                 RenderInline {FONT} at (0,0) size 735x45
                   RenderText {#text} at (0,0) size 735x30
                     text run at (0,0) width 735: "Mayne Island is one of the southern Gulf Islands, off the coast of British Columbia, Canada, between Vancouver and Vancouver"
                     text run at (0,15) width 39: "Island."
-                  RenderBR {BR} at (38,27) size 1x0
+                  LayoutBR {BR} at (38,27) size 1x0
                   RenderText {#text} at (0,30) size 86x15
                     text run at (0,30) width 86: "(See map: left)"
               RenderBlock {P} at (5,125) size 760x75
                 RenderInline {FONT} at (0,0) size 739x75
                   RenderText {#text} at (0,0) size 739x30
                     text run at (0,0) width 739: "Pacific Shore Properties specializes in the diverse properties of the Southern Gulf Islands; which include Beach, Business, View,"
                     text run at (0,15) width 257: "Acreage, Home, Retirement and Recreation."
-                  RenderBR {BR} at (256,27) size 1x0
-                  RenderBR {BR} at (0,30) size 0x15
+                  LayoutBR {BR} at (256,27) size 1x0
+                  LayoutBR {BR} at (0,30) size 0x15
                   RenderText {#text} at (0,45) size 714x30
                     text run at (0,45) 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 (0,60) width 250: "expertise on the Gulf Islands is unmatched."
               RenderBlock {P} at (5,216) size 760x0
           LayoutTableRow {TR} at (0,131) size 772x129
           LayoutTableRow {TR} at (0,261) size 772x131
           LayoutTableRow {TR} at (0,393) size 772x131