Finish JavaScript side of automated end-to-end tests for extension.

Fix issues that arose (primarily, the security origin needing to be
a valid URL without path, not just a hostname).

Add a message client code can send to determine if the component
extension is available.

Add a way to cancel desktop media chooser in case needed.

Add a way to set upload to default to false, not just to true, in
case needed.

BUG=291271
TBR=nkostylev@chromium.org

Review URL: https://codereview.chromium.org/56033003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232609 0039d316-1c4b-4281-b951-d872f2087c98
[Android]: Only kill 'adb' during device status check, not all commands with adb in command line.

This was causing the perf tests to fail since the bb_device_steps_internal.py
had '--adb-root' as an argument and so was being accidentially killed during
the device status check.

BUG=312285

Review URL: https://codereview.chromium.org/56063002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232610 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232610