Tests that the SourceMap header is reported on Debugger.scriptParsed events
Script parsed event:
  - url: http://devtools.test:8000/inspector-protocol/resources/source-map-module.php
  - sourceMapURL: http://localhost/source.js.map
Script parsed event:
  - url: http://devtools.test:8000/inspector-protocol/resources/source-map-module.php
  - sourceMapURL: http://localhost/source.js.map