Bug 786207. Display name in share panel is white on gray on OSX. r=felipe

browser/base/content/browser.xul

@@ -230,7 +230,7 @@
                  aria-label="&social.sharePopup.portrait.arialabel;"/>
         </vbox>
         <vbox id="editSharePopupText">
-          <button id="socialUserDisplayName"
+          <button id="socialUserDisplayName" pack="start"
                   oncommand="SocialUI.showProfile();"/>
           <spacer flex="1"/>
           <label id="socialUserRecommendedText"

browser/themes/pinstripe/browser.css

@@ -1261,11 +1261,10 @@ window[tabsontop="false"] richlistitem[type~="action"][actiontype="switchtab"][s
 
 #socialUserDisplayName {
   -moz-appearance: none;
-  color: #fff;
   border: none;
   background-color: transparent;
-  margin-top: 0;
-  padding-top: 0;
+  margin: 1px;
+  padding: 0;
   font-size: 130%;
   font-weight: bold;
 }