spellCheck and readOnly

Do you want to request a feature or report a bug? Bug What is the current behavior? I have a toggle to change draftjs window from editable to readonly. My editor is setup like so:

  <Editor
      editorState = {editorState}
      onChange = {this.onChange}
      handleKeyCommand={this.handleKeyCommand}
      onTab={this.onTab}
      spellCheck={!this.readOnly}
      readOnly={this.readOnly}
  />

The spell check works in editing mode (not-readonly). But when in readOnly mode (when the spellCheck should be disabled) it still shows spelling error.

**If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem. You can use this jsfiddle to get started:

https://jsfiddle.net/q6ko96mv/1/

What is the expected behavior?

Spell check should be hidden.

Which versions of Draft.js, and which browser / OS are affected by this issue? Did this work in previous versions of Draft.js?

0.9.1