Switches to a Skia-specific appengine entry point that uses condensed data and taskqueue writes.

Switches to a Skia-specific appengine entry point that uses condensed data and taskqueue writes (SkipBuildbotRuns).
The default entry /add_point does not handle large data efficiently, so we've seen >30min timeouts for some bots to upload data. We now switch to using /skia_add_points that I'm writing for Skia, so we can condense the data to send to minimum (since all points in each batch have the same revision, platform and config), and dedicate the actual data processing to /skia_write_datastore which is a taskqueue task that has longer timeout and can run at app backend instead of blocking the bots.
Initial testing from my MacBook on Mac 64 bench data via vpn gave only a little more than 1 second for uploading data for one config, about 15 seconds for all 12 configs. That's a big win against 20+ minutes.
Committed: https://code.google.com/p/skia/source/detail?r=8560

[benchen, 2013-04-08 14:14:28]

Will submit the change to appengine entry url together with this change.

[borenet, 2013-04-08 14:52:32]

LGTM, with the assumption that you've set up your appengine app to deal with the
new data format.

[benchen, 2013-04-08 14:57:45]

Committed patchset #2 manually as r8560 (presubmit successful).