Reviewed by Sam Weinig.

        More work on the new drawing area implementation
        https://bugs.webkit.org/show_bug.cgi?id=52302

        * Platform/Region.cpp:
        (WebKit::Region::Shape::segments_end):
        segments_end could end up returning an iterator that is one element past the Vector data, so
        we can't use operator[] since that will assert.

        * WebProcess/WebPage/DrawingAreaImpl.cpp:
        (WebKit::DrawingAreaImpl::DrawingAreaImpl):
        Initialize the timer.

        (WebKit::DrawingAreaImpl::setNeedsDisplay):
        Unite the rect with the dirty region and schedule a display.

        (WebKit::DrawingAreaImpl::setSize):
        Tell the web page to resize.

        (WebKit::DrawingAreaImpl::scheduleDisplay):
        Start a display timer if needed.

        (WebKit::DrawingAreaImpl::display):
        Add a stub.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@75620 268f45cc-cd09-0410-ab3c-d52691b4dbfc