1. @DomName('XMLHttpRequest.overrideMimeType')
  2. @DocsEditable()
  3. @SupportedBrowser(SupportedBrowser.CHROME)
  4. @SupportedBrowser(SupportedBrowser.FIREFOX)
  5. @SupportedBrowser(SupportedBrowser.SAFARI)
void overrideMimeType(String mime)

Specify a particular MIME type (such as text/xml) desired for the response.

This value must be set before the request has been sent. See also the list of IANA Official MIME types

Source 

@DomName('XMLHttpRequest.overrideMimeType')
@DocsEditable()
@SupportedBrowser(SupportedBrowser.CHROME)
@SupportedBrowser(SupportedBrowser.FIREFOX)
@SupportedBrowser(SupportedBrowser.SAFARI)
void overrideMimeType(String mime) => _blink.BlinkXMLHttpRequest.instance
    .overrideMimeType_Callback_1_(this, mime);