GitLab

> Switch to doing user-resizing via system for panels on Mac
> 
> We used to track and handle user-resizing by ourselves. This brings up a few problems and makes the user-resizing hard to use on Mac. For example, the user-resizing could not be triggered outside or on the edge. Switching to doing it via system solve all these problems.
> 
> Also removed EnableResizeByMouse which is not really used in our code.
> 
> BUG=282652,282657
> TEST=manual test by user-resizing panels
> 
> Review URL: https://chromiumcodereview.appspot.com/23918002

TBR=jianli@chromium.org

Review URL: https://codereview.chromium.org/23922003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221674 0039d316-1c4b-4281-b951-d872f2087c98