Reviewed by Maciej.

        - http://bugs.webkit.org/show_bug.cgi?id=15606
          make cut-off for sparse vs. dense arrays smarter for speed with large arrays

        Makes the morph test in SunSpider 26% faster, and the overall
        benchmark 3% faster.

        This also fixes some small problems we had with the distinction
        between nonexistent and undefined values in arrays.

        * kjs/array_instance.h: Tweaked formatting and naming.
        * kjs/array_instance.cpp: Copied from kjs/array_object.cpp.
        (KJS::storageSize): Added. Computes the size of the storage given a vector length.
        (KJS::increasedVectorLength): Added. Implements the rule for resizing the vector.
        (KJS::isDenseEnoughForVector): Added.
        (KJS::ArrayInstance::ArrayInstance): Initialize the new fields.
        (KJS::ArrayInstance::~ArrayInstance): Since m_storage is now never 0, delete it.
        (KJS::ArrayInstance::getItem): Updated for name changes.
        (KJS::ArrayInstance::lengthGetter): Ditto.
        (KJS::ArrayInstance::inlineGetOwnPropertySlot): Added. Allows both versions of
        getOwnPropertySlot to share more code.
        (KJS::ArrayInstance::getOwnPropertySlot): Just refactored, no code change.
        (KJS::ArrayInstance::put): Added logic for extending the vector as long as the
        array is dense enough. Also keep m_numValuesInVector up to date.
        (KJS::ArrayInstance::deleteProperty): Added code to keep m_numValuesInVector
        up to date.
        (KJS::ArrayInstance::getPropertyNames): Fixed bug where this would omit names
        for array indices with undefined values.
        (KJS::ArrayInstance::increaseVectorLength): Renamed from resizeStorage. Also
        simplified to only handle getting larger.
        (KJS::ArrayInstance::setLength): Added code to update m_numValuesInVector, to
        zero out the unused part of the vector and to delete the map if it's no longer
        needed.
        (KJS::ArrayInstance::mark): Tweaked formatting.
        (KJS::compareByStringForQSort): Ditto.
        (KJS::ArrayInstance::sort): Ditto.
        (KJS::CompareWithCompareFunctionArguments::CompareWithCompareFunctionArguments):
        Ditto.
        (KJS::compareWithCompareFunctionForQSort): Ditto.
        (KJS::ArrayInstance::compactForSorting): Fixed bug where this would turn
        undefined values into nonexistent values in some cases.

        * kjs/array_object.h: Removed MAX_ARRAY_INDEX.
        * kjs/array_object.cpp: Removed ArrayInstance. Moved to a separate file.

        * JavaScriptCore.pri: Added array_instance.cpp.
        * JavaScriptCore.xcodeproj/project.pbxproj: Ditto.
        * kjs/AllInOneFile.cpp: Ditto.

LayoutTests:

        * fast/js/kde/resources/Array.js: Added tests to cover missing value behavior
        (not the same as undefined values in arrays). This matches the ECMA JavaScript
        specification, but doesn't exactly match Firefox.
        * fast/js/kde/Array-expected.txt: Updated with results.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@26881 268f45cc-cd09-0410-ab3c-d52691b4dbfc