This should behave similar to how Xcode behaves: you select a frame in the stack list, and that shows the relevant source file and indicates the line where execution is up to in that stack frame.
Created attachment 9784 [details] Patch
Comment on attachment 9784 [details] Patch r=me
Landed in r15725.
Closing since Drosera has been replaced by the new Web Inspector debugger. Moving to the New Bugs component so the Drosera component can be closed and removed.