Revert "Handle addition/removal of ‘gutter-hidden’ attribute"

This reverts commit 6926236268.

There seems to be some bug or timing issue that prevents the
attachedCallback from being called in all cases when the
attributeChangedCallback is defined. We can figure this out at
a later time.

spec/text-editor-element-spec.coffee

@@ -30,17 +30,6 @@ describe "TextEditorElement", ->
       element = jasmineContent.firstChild
       expect(element.getModel().getText()).toBe 'testing'
 
-  describe "when attributes change", ->
-    it "honors addition/removal of the 'gutter-hidden' attribute", ->
-      element = new TextEditorElement
-      expect(element.getModel().isGutterVisible()).toBe true
-
-      element.setAttributeNode(document.createAttribute("gutter-hidden"))
-      expect(element.getModel().isGutterVisible()).toBe false
-
-      element.removeAttribute('gutter-hidden')
-      expect(element.getModel().isGutterVisible()).toBe true
-
   describe "when the model is assigned", ->
     it "adds the 'mini' attribute if .isMini() returns true on the model", ->
       element = new TextEditorElement

src/text-editor-element.coffee

@@ -71,10 +71,6 @@ class TextEditorElement extends HTMLElement
     @unmountComponent()
     @emitter.emit("did-detach")
 
-  attributeChangedCallback: (name, oldValue, newValue) ->
-    if name is 'gutter-hidden'
-      @getModel().setGutterVisible(not @hasAttribute('gutter-hidden'))
-
   initialize: (model) ->
     @setModel(model)
     this