Plumbs through screen size and scale factor to html_viewer

Plumbs through screen size and scale factor to html_viewer

As ResourceBundle uses the scale factor we gate loading until we know
the scale factor.

I also made it so ViewportMetrics::device_scale_factor is 0 until we have a real value. This way ViewManager clients have a way to know when the real value is available.

BUG=none
TEST=none
R=ben@chromium.org

Committed: https://crrev.com/9d3889610425bb8de984ce1393633267f438c490
Cr-Commit-Position: refs/heads/master@{#329514}

[Ben Goodger (Google), 2015-05-12 21:50:03]

lgtm

[sky, 2015-05-12 21:52:12]

The CQ bit was checked by sky@chromium.org

[commit-bot: I haz the power, 2015-05-12 21:53:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1136743003/1

[commit-bot: I haz the power, 2015-05-12 22:26:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-12 22:28:46]

Patchset 1 (id:??) landed as
https://crrev.com/9d3889610425bb8de984ce1393633267f438c490
Cr-Commit-Position: refs/heads/master@{#329514}