Aggressively delete memory references to reduce memory usage.
Aggressively delete memory references to reduce memory usage.

This works around 'Exceeded soft private memory limit'.

R=csharp@chromium.org
BUG=


Review URL: https://chromiumcodereview.appspot.com/11545004

git-svn-id: 8fa0a038c61565a87d0885d584517a2e12819dac@172414 0039d316-1c4b-4281-b951-d872f2087c98

madecoste/swarming,luci/luci-py,madecoste/swarming,pombreda/swarming,pombreda/swarming,pombreda/swarming,madecoste/swarming,luci/luci-py,luci/luci-py,luci/luci-py,madecoste/swarming,pombreda/swarming