[Tizen][Temp] 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 Chromium r235967 is not within chromium-crosswalk code base.
Merge pull request #1325 from pozdnyakov/Force_Device_Scale

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