Since we're using neither Quirks::shouldMousemoveEventHandlingPreventDefault() nor the MousemoveEventHandlingPreventsDefaultEnabled internal setting, we should remove them.
<rdar://problem/49124334>
Created attachment 365964 [details] Patch
Committed r243499: <https://trac.webkit.org/changeset/243499>
Committed r243504: <https://trac.webkit.org/changeset/243504>