Restrict CORS wildcard+credentials combination for http(s) only.

CORS-with-credentials are only defined for http(s) resources.

Chromium uses Access-Control-Allow-Origin: * with the intention of
whitelisting resources at certain origins for use in XMLHttpRequest and
images with canvas.
When the includeCredentials flag is set, these requests are blocked, even
though the term "credentials" makes no sense for data:/chrome-extension:-URLs.

This CL relaxes the wildcard check for non-http(s) resources, so that implementors
can choose to use CORS regardless of whether credentials were requested.

BUG=315152
TEST=Layout tests are already in CL https://codereview.chromium.org/54173002/

Review URL: https://codereview.chromium.org/192573011

git-svn-id: svn://svn.chromium.org/blink/trunk@169391 bbb929c8-8fbe-4397-9dbb-9b2b20218538