Load base stylesheets on ThemeManager construction

src/atom.coffee

@@ -558,8 +558,6 @@ class Atom extends Model
       console.warn error.message if error?
 
     @config.load()
-    @themes.loadBaseStylesheets()
-
     @setBodyPlatformClass()
     document.head.appendChild(new StylesElement)
     @windowEventHandler = new WindowEventHandler(this)

src/theme-manager.coffee

@@ -17,6 +17,7 @@ class ThemeManager
     @packageManager.registerPackageActivator(this, ['theme'])
     @packageManager.onDidActivateInitialPackages =>
       @onDidChangeActiveThemes => @packageManager.reloadActivePackageStyleSheets()
+    @loadBaseStylesheets()
 
   ###
   Section: Event Subscription