Activate stylesheets from deferred deserializer

spec/atom-spec.coffee

@@ -11,11 +11,13 @@ describe "the `atom` global", ->
       describe "when the package has deferred deserializers", ->
         it "requires the package's main module if one of its deferred deserializers is referenced", ->
           pack = atom.loadPackage('package-with-activation-events')
+          spyOn(pack, 'activateStylesheets').andCallThrough()
           expect(pack.mainModule).toBeNull()
           object = deserialize({deserializer: 'Foo', data: 5})
           expect(pack.mainModule).toBeDefined()
           expect(object.constructor.name).toBe 'Foo'
           expect(object.data).toBe 5
+          expect(pack.activateStylesheets).toHaveBeenCalled()
 
     describe ".unloadPackage(name)", ->
       describe "when the package is active", ->

src/atom-package.coffee

@@ -82,9 +82,12 @@ class AtomPackage extends Package
     @configActivated = true
 
   activateStylesheets: ->
+    return if @stylesheetsActivated
+
     type = if @metadata.theme then 'theme' else 'bundled'
     for [stylesheetPath, content] in @stylesheets
       atom.themes.applyStylesheet(stylesheetPath, content, type)
+    @stylesheetsActivated = true
 
   activateResources: ->
     keymap.add(keymapPath, map) for [keymapPath, map] in @keymaps
@@ -196,7 +199,9 @@ class AtomPackage extends Package
 
   registerDeferredDeserializers: ->
     for deserializerName in @metadata.deferredDeserializers ? []
-      registerDeferredDeserializer deserializerName, => @requireMainModule()
+      registerDeferredDeserializer deserializerName, =>
+        @activateStylesheets()
+        @requireMainModule()
 
   subscribeToActivationEvents: ->
     return unless @metadata.activationEvents?