Fix a flaky download test

The test fails because we call DownloadManager::GetAllDownloads() too fast.
Change the ordering for the dangerous download to start first, then call
DownloadManager::GetAllDownloads().

BUG=948223

Change-Id: I60a73eb138598fc90afaed9fc991e634b30f52dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1546065
Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Xing Liu <xingliu@chromium.org>
Commit-Queue: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#647053}
1 file changed