Reviewed by Kent Tamura.

        Replace isNodeInTextFormControl(Node*) by enclosingTextFormControl(const Position&)
        https://bugs.webkit.org/show_bug.cgi?id=63672

        Replaced isNodeInTextFormControl(Node*) by enclosingTextFormControl(const Position&).
        Also added a safe toTextFormControl to HTMLFormControlElement.h.

        * editing/DeleteSelectionCommand.cpp:
        (WebCore::DeleteSelectionCommand::doApply): Calls enclosingTextFormControl instead of manually
        checking the tag name of shadowAncestorNode.
        * editing/Editor.cpp:
        (WebCore::Editor::selectionForCommand): Rewritten using enclosingTextFormControl and toTextFormControl.
        (WebCore::Editor::cut): Calls enclosingTextFormControl instead of isNodeInTextFormControl.
        (WebCore::Editor::copy): Ditto.
        (WebCore::Editor::setBaseWritingDirection): Calls toTextFormControl instead of manually checking tag name.
        * editing/FrameSelection.cpp:
        (WebCore::FrameSelection::isInPasswordField): Calls enclosingTextFormControl.
        * editing/ReplaceSelectionCommand.cpp:
        (WebCore::ReplaceSelectionCommand::doApply): Ditto.
        * editing/htmlediting.cpp:
        (WebCore::enclosingTextFormControl): Added.
        * editing/htmlediting.h:
        * html/HTMLFormControlElement.h:
        (WebCore::toTextFormControl): Added.
        * page/DragController.cpp:
        (WebCore::DragController::startDrag): Calls enclosingTextFormControl instead of isNodeInTextFormControl.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@90098 268f45cc-cd09-0410-ab3c-d52691b4dbfc