Make blur event on text editor element work with shadow DOM disabled

When the shadow DOM is enabled, this happens organically because the
focus is abstracted across the shadow boundary. Without that abstraction
boundary, we need to pretend that a blur of the hidden input is actually
a blur of the entire editor.

Signed-off-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

src/text-editor-element.coffee

@@ -95,6 +95,7 @@ class TextEditorElement extends HTMLElement
       lineOverdrawMargin: @lineOverdrawMargin
     )
     @component = React.renderComponent(@componentDescriptor, @rootElement)
+    @component.refs.input.getDOMNode().addEventListener 'blur', => @dispatchEvent(new FocusEvent('blur', bubbles: false))
 
   unmountComponent: ->
     return unless @component?.isMounted()