Sets $HOME for PPAPI plugin in ChromeOS.

crbug.com/333031 is trying to remove $HOME in ChromeOS chrome.
This is mostly done but some plugins (like gtalk) rely on
$HOME actually. Thus, sets $HOME in PPAPI plugin runner.

See also: crbug.com/335290

BUG=335290, 333031
R=jhorwich@chromium.org, jorgelo@chromium.org

Review URL: https://codereview.chromium.org/132053007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246490 0039d316-1c4b-4281-b951-d872f2087c98
[Telemetry] Remove a python 2.7 backfill.

According to issue 304190, we can now rely on python 2.7 on all the bots. This
change is to verify that. Please revert it if any bot breaks. If successful, we
can do a lot of similar cleanups.

BUG=304190

Review URL: https://codereview.chromium.org/145393002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246491 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246490
SVN changes up to revision 246491