Fix regions generation on windows.

On windows HRGN for window is generated from the SkPath using dumb
function that doesn`t respects anything except simple polygons. It's
impossible to create window with round corners on windows. Replacing
implementation of that function with a new one will fix this.

R=asvitkine@chromium.org

BUG=322360

Review URL: https://codereview.chromium.org/673623002

Cr-Commit-Position: refs/heads/master@{#304045}
6 files changed