Seen here:
https://ci.chromium.org/buildbot/tryserver.chromium.android/linux_android_rel_ng/419326

on a failed tryjob from this unrelated CL:
https://chromium-review.googlesource.com/c/chromium/src/+/745966

Stack trace:

java.lang.RuntimeException: An error occured while executing doInBackground()
	at android.os.AsyncTask$3.done(AsyncTask.java:300)
	at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
	at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
	at java.util.concurrent.FutureTask.run(FutureTask.java:242)
	at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
	at java.lang.Thread.run(Thread.java:841)
Caused by: java.lang.NullPointerException
	at org.chromium.chrome.browser.download.DownloadInfo.getUserAgent(DownloadInfo.java:91)
	at org.chromium.chrome.browser.download.OMADownloadHandler$PostStatusTask.doInBackground$5f8445a4(OMADownloadHandler.java:926)
	at org.chromium.chrome.browser.download.OMADownloadHandler$PostStatusTask.doInBackground(OMADownloadHandler.java:902)
	at android.os.AsyncTask$2.call(AsyncTask.java:288)
	at java.util.concurrent.FutureTask.run(FutureTask.java:237)
	... 4 more
Searching for native crashes in: /b/swarming/w/itkfNZ6m/tmpe5gDz4
Unknown Android release, consider passing --packed-lib.
Reading Android symbols from: /b/swarming/w/ir
Searching for Chrome symbols from within: /b/swarming/w/ir/out/Release/lib.unstripped:/b/swarming/w/ir/out/Release/lib:/b/swarming/w/ir/out/Release


Please investigate.