Remove getApplicationContext calls from download

Continuation of work in bug 646094.

Preparing to activate an errorprone check to flag
context#getApplicationContext calls. The goal is to prevent storing the
resulting context as a class property, and instead use ContextUtils.

Bug: 846456
Change-Id: Id9b03bc842f60c805b59c2a9eade386e1a55bcf8
Reviewed-on: https://chromium-review.googlesource.com/1095989
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Tiger Oakes <tigero@google.com>
Cr-Commit-Position: refs/heads/master@{#576848}
15 files changed