[evita] ui: Introduce |ArrowButton|, |Button| and |ButtonListener|. They are extracted from "evita/views/tab_strip.cc".
[evita] gfx: Introduce |gfx::PointF::Offset(float delta_x, float delta_y) => gfx::Point|.
[evita] views: Shrink tab strip height to 28px from 32px.
[evita] gfx: Introduce |gfx::Canvas::SetOffsetBounds(gfx::RectF)| for replacement of |gfx::Canvas::SetOffset(gfx::PointF)|.
Merge branch 'master' of https://github.com/eval1749/evita