2010-10-01 Ryosuke Niwa <rniwa@webkit.org>

      Reviewed by Darin Adler.

        FormatBlockCommand and IndentOutdentCommand should use the same code to iterate paragraphs
        https://bugs.webkit.org/show_bug.cgi?id=46840

        Added ApplyBlockElementCommand, which is an abstract class inherited by FormatBlockCommand
        and IndentOutdentCommand.  It is intended to be inherited by InsertListCommand as well.

        ApplyBlockElementCommand's doApply verifies the current selection and exits early
        if it's invalid or orphaned or if the current selection is outside editable region.
        It then calls formatSelection to apply the block element after which doApply restores the selection.
        formatSelection iterates through paragraphs and calls formatParagraph, a pure virtual function
        implemented by FormatBlockCommand and IndentOutdentCommand, on each paragraph.

        No new tests are added since this is a refactoring.

        * Android.mk: Added ApplyBlockElementCommand.cpp.
        * CMakeLists.txt: Ditto.
        * GNUmakefile.am: Added ApplyBlockElementCommand.cpp and ApplyBlockElementCommand.h.
        * WebCore.gypi: Ditto.
        * WebCore.pro: Ditto.
        * WebCore.xcodeproj/project.pbxproj: Ditto.
        * editing/ApplyBlockElementCommand.cpp: Added.
        (WebCore::countParagraphs): Moved from IndentOutdentCommand.cpp
        (WebCore::ApplyBlockElementCommand::ApplyBlockElementCommand): Added.
        (WebCore::ApplyBlockElementCommand::doApply): Moved from IndentOutdentCommand::doApply.
        (WebCore::ApplyBlockElementCommand::formatSelection): Moved from IndentOutdentCommand::indentRegion.
        (WebCore::ApplyBlockElementCommand::createBlockElement): Added.
        (WebCore::ApplyBlockElementCommand::splitTextNodes): Moved from IndentOutdentCommand::splitTextNodes.
        * editing/ApplyBlockElementCommand.h: Added.
        * editing/EditingAllInOne.cpp:
        * editing/EditorCommand.cpp:
        (W