Fix 55832: css "width: 100%" rendering incorrectly for button elements. patch by djoham@criadvantage.com. r=ianh a=ben, rtm++

layout/html/document/src/html.css

@@ -662,6 +662,7 @@ input[type="submit"] {
   font: button;
   cursor: default;
   white-space: pre;
+  -moz-box-sizing: border-box;
   -moz-user-select: none;
   -moz-binding: none;
 }

layout/style/html.css

@@ -662,6 +662,7 @@ input[type="submit"] {
   font: button;
   cursor: default;
   white-space: pre;
+  -moz-box-sizing: border-box;
   -moz-user-select: none;
   -moz-binding: none;
 }