Changed the test case to get it inline with the intended behavior 

The expected results match because the Render Image will return a size with the alternate content. The test case had an additional "/" in the file path, which lead to a failed load, whereas the Author intention was to to load it (I guess!).

BUG=

Review URL: https://chromiumcodereview.appspot.com/24021006

git-svn-id: svn://svn.chromium.org/blink/trunk@157475 bbb929c8-8fbe-4397-9dbb-9b2b20218538