Serialize root view state to a string of JSON when storing it on the window upon refresh

This avoid situations where arrays in the window state pointed to a different constructor than the current context's Array constructor.

spec/app/window-spec.coffee

@@ -53,7 +53,7 @@ describe "Window", ->
       expect(atom.rootViewStates[$windowNumber]).toBeUndefined()
       expectedState = window.rootView.serialize()
       $(window).trigger 'beforeunload'
-      expect(atom.rootViewStates[$windowNumber]).toEqual expectedState
+      expect(atom.rootViewStates[$windowNumber]).toEqual JSON.stringify(expectedState)
 
     it "unsubscribes from all buffers", ->
       editor1 = rootView.activeEditor()

src/app/root-view.coffee

@@ -85,7 +85,7 @@ class RootView extends View
     extension.activate(this, @extensionStates[extension.name])
 
   deactivate: ->
-    atom.rootViewStates[$windowNumber] = @serialize()
+    atom.rootViewStates[$windowNumber] = JSON.stringify(@serialize())
     extension.deactivate?() for name, extension of @extensions
     @remove()
 

src/app/window.coffee

@@ -41,7 +41,7 @@ windowAdditions =
   attachRootView: (pathToOpen) ->
     rootViewState = atom.rootViewStates[$windowNumber]
     if rootViewState
-      @rootView = RootView.deserialize(rootViewState)
+      @rootView = RootView.deserialize(JSON.parse(rootViewState))
     else
       @rootView = new RootView(pathToOpen)
       @rootView.open() unless pathToOpen