Rendering with device scale factor for high DPI, https://bugs.webkit.org/show_bug.cgi?id=196339, requires re-scaling on dynamic device scale factor changes, e.g. moving a window between different displays. The appropriate winapi message to do this is WM_DPICHANGED, that MainWindow handles on https://github.com/WebKit/WebKit/blob/d48be59b226a3da86b16e3948e08db42c6637263/Tools/MiniBrowser/win/MainWindow.cpp#L392. But it couldn't be caught on WebView. We need to propagate WM_DPICHANGED from MainWindow to WebView.
<rdar://problem/128777848>
We noticed it's not necessary to propagate WM_DPICHANGED, we can do on WM_SIZE instead. I renamed title.
Pull request: https://github.com/WebKit/WebKit/pull/29810
Committed 280003@main (50c1741732a3): <https://commits.webkit.org/280003@main> Reviewed commits have been landed. Closing PR #29810 and removing active labels.