tast-tests: remove encoded video when the test passes.

We shall only need to investigate encoded video when a video.EncodeAccel
test fail. Remove the output file to shrink test artifact.

BUG=chromium:980445
TEST=Run video.EncodeAccel* test.

Change-Id: Ib555f345417fa36b868fe25b1fd911e2fc35126e
Reviewed-on: https://chromium-review.googlesource.com/1728497
Tested-by: Shuo-Peng Liao <deanliao@chromium.org>
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
(cherry picked from commit 402f52ee0840a788fb28b3830f05cb491c0ae97e)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/tast-tests/+/1776504
Commit-Queue: Shuo-Peng Liao <deanliao@chromium.org>
diff --git a/src/chromiumos/tast/local/bundles/cros/video/encode/accel_video.go b/src/chromiumos/tast/local/bundles/cros/video/encode/accel_video.go
index b5caee5..93f7249 100644
--- a/src/chromiumos/tast/local/bundles/cros/video/encode/accel_video.go
+++ b/src/chromiumos/tast/local/bundles/cros/video/encode/accel_video.go
@@ -177,6 +177,10 @@
 				s.Fatalf("Failed to run %v: %v", exec, err)
 			}
 		}
+		// Only keep the encoded result when there's something wrong.
+		if err := os.Remove(outPath); err != nil {
+			s.Log("Failed to remove output file: ", err)
+		}
 	}
 }