Compute the base dpi from X

X uses 96 as default, and alters the screen size
but it can be overwritten. Compute the dpi from X
to match what gtk sues as base.

Round the dsf to 1 decimals as finer grained value can cause rendering problem than benefit.

Gpu test expectation on nvidia needs to be updated, so mark these tests as failing now.

BUG=485183

Review URL: https://codereview.chromium.org/1136913005

Cr-Commit-Position: refs/heads/master@{#330212}
3 files changed