Reviewed by Hyatt.

    Reviewed by Hyatt.

        Optimize linebox memory consumption:
        - move all bitfields to baseclass compacting them
        - make InlineTextBox::m_truncation unsigned short and make it relative to m_start
        - remove extremely rarely used EllipsisBox pointer from RootInlineBox and instead
          use a global hashmap to store it if needed
        - use minimum required number of bits to store BidiStatus enum variables in RootInlineBox
        - move overflow variables in RootInlineBox to a separate struct that is instantiated
          only if any of the variables is set to a value that can't trivially be derived from
          box x, y, width and height

        As a result line box objects shrink:
            InlineBox: 44 -> 44 bytes
            InlineTextBox: 68 -> 60 bytes
            InlineFlowBox: 68 -> 64 bytes
            RootInlineBox: 128 -> 88 bytes

        The optimizations possiblity was noticed when debugging http://bugs.webkit.org/show_bug.cgi?id=12833
        Bug 12833: REGRESSION: Selecting text in 6.6MB txt file is sluggish as of the Feb 19th nightly
        <rdar://problem/5028159>

        On that page the patch saves 11.5MB or some 21% of linebox memory consumption. It also
        actually improves selection performance somewhat by improving memory locality.

        * rendering/InlineBox.h:
        (WebCore::InlineBox::InlineBox):
        * rendering/InlineFlowBox.h:
        (WebCore::InlineFlowBox::InlineFlowBox):
        * rendering/InlineTextBox.cpp:
        (WebCore::InlineTextBox::placeEllipsisBox):
        (WebCore::InlineTextBox::nodeAtPoint):
        (WebCore::InlineTextBox::paint):
        (WebCore::InlineTextBox::paintDecoration):
        (WebCore::InlineTextBox::paintSpellingOrGrammarMarker):
        (WebCore::InlineTextBox::paintMarkedTextUnderline):
        * rendering/InlineTextBox.h:
        (WebCore::InlineTextBox::InlineTextBox):
        * rendering/RootInlineBox.cpp:
        (WebCore::throw):
        (WebCore::RootInlineBox::Overflow::operator delete):
        (WebCore::RootInlineBox::Overflow::destroy):
        (WebCore::RootInlineBox::destroy):
        (WebCore::RootInlineBox::detachEllipsisBox):
        (WebCore::RootInlineBox::clearTruncation):
        (WebCore::RootInlineBox::placeEllipsis):
        (WebCore::RootInlineBox::paintEllipsisBox):
        (WebCore::RootInlineBox::addHighlightOverflow):
        (WebCore::RootInlineBox::nodeAtPoint):
        (WebCore::RootInlineBox::adjustPosition):
        (WebCore::RootInlineBox::selectionTop):
        (WebCore::RootInlineBox::setLineBreakInfo):
        (WebCore::RootInlineBox::ellipsisBox):
        (WebCore::RootInlineBox::setVerticalOverflowPositions):
        (WebCore::RootInlineBox::setHorizontalOverflowPositions):
        (WebCore::RootInlineBox::setVerticalSelectionPositions):
        * rendering/RootInlineBox.h:
        (WebCore::RootInlineBox::RootInlineBox):
        (WebCore::RootInlineBox::topOverflow):
        (WebCore::RootInlineBox::bottomOverflow):
        (WebCore::RootInlineBox::leftOverflow):
        (WebCore::RootInlineBox::rightOverflow):
        (WebCore::RootInlineBox::lineBreakBidiStatus):
        (WebCore::RootInlineBox::selectionBottom):
        (WebCore::RootInlineBox::Overflow::Overflow):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@20103 268f45cc-cd09-0410-ab3c-d52691b4dbfc