I need to measure loading time of each component of web page ( css, javascripts, ajax request, including each resource with GET and POST methods. This could be done and watched through Chrome's inspect element or httpwatch or other software but I need something which could pass variables to post request using scripts and then could measure everything happening under that request.
The other thing is that I needed to monitor external website, and therefore I dont have control over webpages where I could write my own code around each load, unload call to measure total time consumed on page itself
Have a look at http://code.google.com/p/pcaphar/ or http://pcapperf.appspot.com/
You can use bog-standard testing tools to script the tests, then run Wireshark, tcpdump etc. to capture the traffic to a pcap file while the test executes.
Use one of the above tools to generate the HARs and then you can analyse them using the various tools available.