[XMLHttpRequest] overrideMimeType(mime) does not update the response's "Content-Type" header
https://bugs.webkit.org/show_bug.cgi?id=98137

Patch by Christophe Dumez <christophe.dumez@intel.com> on 2012-10-02
Reviewed by Kentaro Hara.

Source/WebCore:

According to the XMLHttpRequest specification, overrideMimeType(mime) sets the
"Content-Type" header for the response to mime. However, with the current
implementation, calling overrideMimeType(mime) does not affect the value
returned by client.getResponseHeader("Content-Type"). This patch makes sure
the response's "Content-Type" header is properly updated with the override
MIME type.

Test: http/tests/xmlhttprequest/xmlhttprequest-overridemimetype-content-type-header.html

* xml/XMLHttpRequest.cpp:
(WebCore::XMLHttpRequest::didReceiveResponse):

LayoutTests:

Add layout test to check that calling overrideMimeType(mime) properly
sets the response's "Content-Type" header to mime.

* http/tests/xmlhttprequest/xmlhttprequest-overridemimetype-content-type-header-expected.txt: Added.
* http/tests/xmlhttprequest/xmlhttprequest-overridemimetype-content-type-header.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk/LayoutTests@130158 268f45cc-cd09-0410-ab3c-d52691b4dbfc