GitLab

This is to clarify why we should not be dispatching synthetic mouse exit events on
Windows.

BUG=394672
R=sky

Review URL: https://codereview.chromium.org/454053004

Cr-Commit-Position: refs/heads/master@{#288970}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288970 0039d316-1c4b-4281-b951-d872f2087c98