[Tizen] Enforce device scale factor value to '2.0' on Tizen

Enforce device scale factor value to '2.0' on Tizen so that viewport meta tag works properly on Tizen devices.
This is a workaround until Aura Linux HIDPI support is in place: https://codereview.chromium.org/27156003/.
Merge pull request #1049 from pozdnyakov/Force_Device_Scale

[Tizen][Temp] Enforce device scale factor value to '2.0' on Tizen