rebaseline_server: cache results in long-running ImageDiffDB instance

rebaseline_server: cache results in long-running ImageDiffDB instance

Rather than rebuilding the ImageDiffDB from scratch every time we update expected/actual results, keep the same ImageDiffDB instance around and add image pairs to it.

This makes updating results within a long-running server.py *much* faster, and tests out an idea I'm ruminating in https://goto.google.com/LongRunningImageDiffDBServer : we could run an ImageDiffDB server that developers could connect to from their locally running rebaseline_server instances, for much faster launch times.

BUG=skia:2414
NOTRY=True

Committed: https://skia.googlesource.com/skia/+/6132b436d8723beaf06d1a8a0880f4f1535908a0

[epoger, 2014-07-08 21:12:30]

Ready for review at patchset 1.

[rmistry, 2014-07-09 13:14:04]

LGTM

https://codereview.chromium.org/379563005/diff/1/gm/rebaseline_server/imagedi...
File gm/rebaseline_server/imagediffdb.py (right):

https://codereview.chromium.org/379563005/diff/1/gm/rebaseline_server/imagedi...
gm/rebaseline_server/imagediffdb.py:224: def get_storage_root(self):
[Optional] Can also do:

@property
def storage_root(self):
  return self._storage_root

http://stackoverflow.com/questions/6618002/python-property-versus-getters-and...

[epoger, 2014-07-09 14:57:36]

Thanks. Committing now.

https://codereview.chromium.org/379563005/diff/1/gm/rebaseline_server/imagedi...
File gm/rebaseline_server/imagediffdb.py (right):

https://codereview.chromium.org/379563005/diff/1/gm/rebaseline_server/imagedi...
gm/rebaseline_server/imagediffdb.py:224: def get_storage_root(self):
On 2014/07/09 13:14:04, rmistry wrote:
> [Optional] Can also do:
> 
> @property
> def storage_root(self):
>   return self._storage_root
> 
>
http://stackoverflow.com/questions/6618002/python-property-versus-getters-and...

Good point.  Fixed this one, and added a TODO for others in this file.

[epoger, 2014-07-09 14:58:12]

The CQ bit was checked by epoger@google.com

[commit-bot: I haz the power, 2014-07-09 14:59:01]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/epoger@google.com/379563005/40001

[commit-bot: I haz the power, 2014-07-09 14:59:10]

Change committed as 6132b436d8723beaf06d1a8a0880f4f1535908a0