So if I add break points in .dart files that are located in /web directory of my project, it works fine. For example I\'m using AngularDart and the main.dart file works. How
I will combine the accepted answer + comment to that answer. Breakpoints 100% works only when you set them for files inside (no domain) category on Sources tab.
As I understand, in category with your domain name they are working only for files that was included with tag. They won't work for imported files.
I have created an issue: Dartium ignores breakpoints set not in (no domain) category.