Bug 1162490 - Only set the transparent accentcolor for Dev Edition theme in Windows;r=Gijs

It is causing the drop shadow to disappear on osx 10.9.  Windows is the only platform
that uses a transparent background on the tabs, so it's the only one that neesd the accentcolor

browser/components/nsBrowserGlue.js

@@ -733,7 +733,9 @@ BrowserGlue.prototype = {
     LightweightThemeManager.addBuiltInTheme({
       id: "firefox-devedition@mozilla.org",
       name: themeName,
+#ifdef XP_WIN
       accentcolor: "transparent",
+#endif
       headerURL: "resource:///chrome/browser/content/browser/defaultthemes/devedition.header.png",
       iconURL: "resource:///chrome/browser/content/browser/defaultthemes/devedition.icon.png",
       author: vendorShortName,