How to configure Single Logout when using Google Apps as the Identity Provider?

As outlined in the Google docs you can use Google Apps as a SAML 2.0 IdP. The IdP metadata includes a URL for SSO, but doesn't contain a SLO URL:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<md:EntityDescriptor xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata" entityID="https://accounts.google.com/o/saml2?idpid=XXXXXXXX" validUntil="xxxxxxx">
  <md:IDPSSODescriptor WantAuthnRequestsSigned="false" protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
    <md:KeyDescriptor use="signing">
      <ds:KeyInfo xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
    <ds:X509Data>
      <ds:X509Certificate>....</ds:X509Certificate>
    </ds:X509Data>
      </ds:KeyInfo>
    </md:KeyDescriptor>
    <md:NameIDFormat>urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress</md:NameIDFormat>
    <md:SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect" Location="https://accounts.google.com/o/saml2/idp?idpid=XXXXXXXXX"/>
    <md:SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"     Location="https://accounts.google.com/o/saml2/idp?idpid=XXXXXXXXX"/>
  </md:IDPSSODescriptor>
</md:EntityDescriptor>

Trying to just use the same URL for SLO results in an error at Google:

Error parsing the request, malformed_request: The SAML request is malformed. That’s all we know.

Of course you can just redirect to https://accounts.google.com/logout but that will only end the Google session.

SLO is not mentioned in Google docs. Is it supported?

Google does not support SAML SLO as an identity or service provider.