Large uploads via the compression proxy fail unexpectedly

[GoogleCodeExporter]

Clients that use the google compression proxy and our online html5 speed test
frequently get errors during the upload phase, when the browser attempts to 
upload a certain (large) amount of data to a target IP address.

The browser XHR2 request fails after a delay where everything seems to be going 
ok
and unfortunately the error is of the readyState == 4 .. status 0 variety which 
indicates a problem but not what the problem is.

An example is that a phone with a user-agent of 

"Mozilla/5.0 (Linux; Android 5.0.1; SAMSUNG-SGH-I337 Build/LRX22C) 
AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.96 Mobile Safari/537.36"

attempts to upload to a URL (http, not https) a 5769894 byte binary blob. The 
target URL receives the
data and returns a status 200 and a short message to 66.249.83.253.

The browser on the phone however returns an error to the javascript without 
details

Wen the data compression proxy is turned off, everything behaves normally.

If I should post this on a different discussion project issue list please tell 
me where.

Original issue reported on code.google.com by [email protected] on 10 May 2015 at 10:18