Add GetCaptionButtonHeightInDIPs() method

This CL adds the the function GetCaptionButtonHeightInDIPs() method that returns
the height of the caption buttons on Windows in DIPs and uses it for the
Windows 10 MD avatar button (see http://crrev.com/2851543002).

BUG=635699

Review-Url: https://codereview.chromium.org/2833363002
Cr-Commit-Position: refs/heads/master@{#470271}
2 files changed