Tests for URL.createObjectURL(mediaSource) in Media Source Extensions.
Fixed the file names and the titles to represent what the test does.
Fixed the test program to check the created URL is a correct Blog URI.
Fixed the titles of the documents and the explanation of what the test does.
Removed unnecessary video elements. If required, it fixed to make video element node by DOM API.
Fixed to throw TypeError when the API don't accept a null value.
Merge pull request #825 from shishimaru/shishimaru/URLObjectExtensions-createObjectURL

Tests for URL.createObjectURL(mediaSource) in Media Source Extensions.