[Tizen] DesktopRootWindowHost factory is not needed.

After Crosswalk revision(08e61f325): Provide our DesktopRootWindowHost using OnBeforeWidgetInit()
DesktopRootWindowHost factory is not needed.
DesktopRootWindowHost factory was made by Intel, and we want to revert it to
minimize chromium changes.

Revert "Add factory mechanism to DesktopRootWindowHost."

This reverts commit 20ac69924e1b16d1e7ff918dce3cc22bd4142d04.
Merge pull request #63 from luxtella/factory

[Tizen] DesktopRootWindowHost factory is not needed.