Image derivative token generation issue

Hello,

There is an issue with itoken generation in image module.
The function image_style_url() allows you to use path or uri.
For example we can use either 'logo_1.gif' or 'public://logo_1.gif'.
However if we use 'logo_1.gif' the token is generated for the path, but the validation always try with URI and this causing itok validation error and you will get "Access denied" page.
I'm attaching a patch for this to use $uri instead of $path in image_style_url() function.