Move power_LoadTest extension over to manifest v2

Telemetry requires all extensions to be manifest v2. This moves javascript out
of html files and into js files. This also reduces the time for the background
window to 60 minutes and fixes a small issue during the end of the extension
loop which delays page load data from being uploaded.

TEST=power_LoadTest
BUG=chromium:337029

Change-Id: I49e61b40ae7a4b177d1ea0395ae2dffbb60ee93b
Previous-Reviewed-on: https://chromium-review.googlesource.com/193053
(cherry picked from commit 7ff242af4e9fa2bd1ea05a64c6c7e07b34339476)
Reviewed-on: https://chromium-review.googlesource.com/193687
Reviewed-by: Todd Broch <tbroch@chromium.org>
Tested-by: Derek Basehore <dbasehore@chromium.org>
7 files changed