Added EditSession.copy()

Also, EditSession only needs a project to be deserialized

src/app/edit-session.coffee

@@ -12,8 +12,8 @@ module.exports =
 class EditSession
   @idCounter: 1
 
-  @deserialize: (state, editor, rootView) ->
-    session = rootView.project.open(state.buffer)
+  @deserialize: (state, project) ->
+    session = project.open(state.buffer)
     session.setScrollTop(state.scrollTop)
     session.setScrollLeft(state.scrollLeft)
     session.setCursorScreenPosition(state.cursorScreenPosition)
@@ -65,6 +65,9 @@ class EditSession
     scrollLeft: @getScrollLeft()
     cursorScreenPosition: @getCursorScreenPosition().serialize()
 
+  copy: ->
+    EditSession.deserialize(@serialize(), @project)
+
   isEqual: (other) ->
     return false unless other instanceof EditSession
     @buffer == other.buffer and

src/app/editor.coffee

@@ -46,7 +46,7 @@ class Editor extends View
   lineOverdraw: 100
 
   @deserialize: (state, rootView) ->
-    editSessions = state.editSessions.map (state) -> EditSession.deserialize(state, editor, rootView)
+    editSessions = state.editSessions.map (state) -> EditSession.deserialize(state, rootView.project)
     editor = new Editor(editSession: editSessions[state.activeEditSessionIndex], mini: state.mini)
     editor.editSessions = editSessions
     editor.isFocused = state.isFocused
@@ -520,8 +520,7 @@ class Editor extends View
       @updateRenderedLines()
 
   newSplitEditor: ->
-    editSession = EditSession.deserialize(@activeEditSession.serialize(), this, @rootView())
-    new Editor { editSession }
+    new Editor { editSession: @activeEditSession.copy() }
 
   splitLeft: ->
     @pane()?.splitLeft(@newSplitEditor()).wrappedView