Add a keep-working-dir flag to generate_coverage script.
Add a keep-working-dir flag to generate_coverage script.

This makes it easier to debug the scripts output.

R=rogerm@chromium.org,chrisha@chromium.org

Review URL: http://codereview.appspot.com/5528097

git-svn-id: db59699583a60be9a535cd09cdc9132301867226@616 15e8cca8-e42c-11de-a347-f34a4f72eb7d

ericmckean/syzygy,sebmarchand/syzygy,supriyantomaftuh/syzygy,ericmckean/syzygy,google/syzygy,google/syzygy,pombreda/syzygy,google/syzygy,pombreda/syzygy,ericmckean/syzygy,Eloston/syzygy,ericmckean/syzygy,supriyantomaftuh/syzygy,wangming28/syzygy,pombreda/syzygy,Eloston/syzygy,pombreda/syzygy,google/syzygy,supriyantomaftuh/syzygy,sebmarchand/syzygy,wangming28/syzygy,sebmarchand/syzygy,sebmarchand/syzygy,pombreda/syzygy,sebmarchand/syzygy,wangming28/syzygy,ericmckean/syzygy,supriyantomaftuh/syzygy,wangming28/syzygy