Called before a child process is launched. Will be called on the browser
process UI thread when launching a render process and on the browser
process IO thread when launching a GPU process. Provides an opportunity to
modify the child process command line. Do not keep a reference to
|command_line| outside of this function.
Called before a child process is launched. Will be called on the browser process UI thread when launching a render process and on the browser process IO thread when launching a GPU process. Provides an opportunity to modify the child process command line. Do not keep a reference to |command_line| outside of this function.