Since BETTERSCROLLING is defined as 1, remove dead code assuming BETTERSCROLLING not defined.
Convert scrdy into fractional math to make division by scrdy more stable (e.g. multiple by scrdy denumonator; divide by scrdy numerator). Subtact out w->km.header when computing the scroolbar area height(vertical area scroll bar slides in) which is used in computing newtop.
Since BETTERSCROLLING is defined as 1, remove dead code assuming BETTERSCROLLING not defined. Convert scrdy into fractional math to make division by scrdy more stable (e.g. multiple by scrdy denumonator; divide by scrdy numerator). Subtact out w->km.header when computing the scroolbar area height(vertical area scroll bar slides in) which is used in computing newtop.