Use atom.workspace.getView to construct WorkspaceViews

It returns the root DOM node of the workspace. Eventually this will
be a custom element but for now it’s just a DOM node with a
__spacePenView reference on it.

benchmark/benchmark-suite.coffee

@@ -7,7 +7,7 @@ describe "editorView.", ->
 
   beforeEach ->
     atom.workspaceViewParentSelector = '#jasmine-content'
-    atom.workspaceView = new WorkspaceView
+    atom.workspaceView = atom.workspace.getView(atom.workspace).__spacePenView
     atom.workspaceView.attachToDom()
 
     atom.workspaceView.width(1024)