title: Cannot set a breakpoint on Angular application
body: <p>On Firefox Quantum (57.0 64-bit), when I try to set a breakpoint on an Angular application using the Debugger pane, the breakpoint immediately disappear and it is not actually set.</p>
  
  <p>See a video of the behavior here: 
  <a href="https://youtu.be/aBQ0wOeIYYQ" rel="nofollow noreferrer">https://youtu.be/aBQ0wOeIYYQ</a></p>
  
  <p>For the video I created a new angular project with angular-cli:</p>
  
  <pre><code>Angular CLI: 1.5.0
  Node: 8.4.0
  OS: darwin x64
  </code></pre>
  
  <p>Then I serve the project using <code>ng serve</code>.</p>
  
  <p>I tried on Chrome and the breakpoint is correctly set.</p>