I put it in ignore file cause the file references user dependent path, and is not necessary to make the sample run in the Dart VM or in a "normal" browser.
Making tests I observe that :
* debuging the project with sourcemap seems to work in Dartium without this file
* debuging the project with sourcemap does not work in Chrome even with the file
It deserves to look deeper but for the moment I do not think it should be commited...