A4A: Remove CSI pings from DOM

[tdrl]

Avoids writing CSI ping beacons to DOM -- now sends them just with new Image(). Maintains dev().info for console messaging in dev mode, though.

[keithwrightbos]

One thing to consider is handling network failure. Take a look at reportingBackoff:
https://github.com/ampproject/amphtml/blob/master/src/error.js#L61

[tdrl]

@keithwrightbos Sure... Seems like a good idea if we wanted to make this service more robust. But, really, do we? I mean, the plan is to deprecate it in favor of amp-analytics anyway. And I don't get a sense that we're missing so many pings that this is a big issue, do you?

[tdrl]

@keithwrightbos Sure... Seems like a good idea if we wanted to make this service more robust. But, really, do we? I mean, the plan is to deprecate it in favor of amp-analytics anyway. And I don't get a sense that we're missing so many pings that this is a big issue, do you?

[keithwrightbos]

SGTM