Reset is_completed_ before attempting a new crx component download.

When downloading a url, the state of the BackgroundDownloader must be
reset.

A better solution later on would be implementing a BitsFetcher that can
only do one download, similar to UrlFetcher. This avoids the situation
when dirty state post-download is carried over to a subsequent
download.

BUG=304354

Review URL: https://codereview.chromium.org/102993014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242108 0039d316-1c4b-4281-b951-d872f2087c98
[Telemetry] Don't restore command lines that will break Chrome.

A common problem is that if something goes wrong with Telemetry, the command
line file which points all network traffic at Web Page Replay can be left in
place which results in users not understanding why no pages will load.

So if we detect this setting, simply clear the file.

BUG=

Review URL: https://codereview.chromium.org/108573008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242109 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242109