Issue #1673 - Part 4: Unprefix -moz-tab-size.

While we do fail a couple of tests, the other mainstream browsers also fail them and I think our implementation of tab-size is good enough to be unprefixed at this point. Having this patch also makes testing easier.

parser/html/nsHtml5ViewSourceUtils.cpp

@@ -31,7 +31,7 @@ nsHtml5ViewSourceUtils::NewBodyAttributes()
   int32_t tabSize = mozilla::Preferences::GetInt("view_source.tab_size", 4);
   if (tabSize > 0) {
     nsString style;
-    style.AssignASCII("-moz-tab-size: ");
+    style.AssignASCII("tab-size: ");
     style.AppendInt(tabSize);
     bodyAttrs->addAttribute(
       nsHtml5AttributeName::ATTR_STYLE, nsHtml5String::FromString(style), -1);