GitLab

BrowserPluginGuest::GetScreenCoordinates and BrowserPluginGuest::ToGuestRect
served very similar purposes, and having both around would probably just
increase the likelihood of bugs cropping up. This CL removes ToGuestRect.

BUG=none

Review URL: https://codereview.chromium.org/554773002

Cr-Commit-Position: refs/heads/master@{#293867}