Clear the stack trace on clear all.
Clear the stack trace on clear all.

BUG= http://code.google.com/p/sawbuck/issues/detail?id=16


git-svn-id: db59699583a60be9a535cd09cdc9132301867226@37 15e8cca8-e42c-11de-a347-f34a4f72eb7d

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