Remove lineprocessor sample.

This sample used to demonstrate the usage of the DebuggerAgent. The latter
has been removed, so this sample has no point anymore.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/754043002

Cr-Commit-Position: refs/heads/master@{#25488}
Disable regress-3717 for gc-stress.

TBR=ulan@chromium.org
BUG=v8:3723
LOG=N

Review URL: https://codereview.chromium.org/749283002

Cr-Commit-Position: refs/heads/master@{#25489}