Make sure normal/bold weight distinction in thread pane works correctly when system fonts are bold. b=101981 r=jag sr=hewitt

themes/classic/messenger/mac/threadPane.css

@@ -30,6 +30,10 @@
 
 /* ::::: thread decoration ::::: */
 
+outlinerbody:-moz-outliner-cell-text(read) {
+  font-weight: normal;
+}
+
 outlinerbody:-moz-outliner-cell-text(unread) {
   font-weight: bold;
 }

themes/classic/messenger/win/threadPane.css

@@ -30,6 +30,10 @@
 
 /* ::::: thread decoration ::::: */
 
+outlinerbody:-moz-outliner-cell-text(read) {
+  font-weight: normal;
+}
+
 outlinerbody:-moz-outliner-cell-text(unread) {
   font-weight: bold;
 }

themes/modern/messenger/threadPane.css

@@ -30,6 +30,10 @@
 
 /* ::::: thread decoration ::::: */
 
+outlinerbody:-moz-outliner-cell-text(read) {
+  font-weight: normal;
+}
+
 outlinerbody:-moz-outliner-cell-text(unread) {
   font-weight: bold;
 }