Reviewed by Kenneth Rohde Christiansen.

        [Qt] Remove CleanupHandler by passing file descriptors.

        Deleting files in signal handler of UI process is not a good idea,
        because the memory where filenames are stored might not be valid
        after a crash.

        To avoid the need of using signal handlers for cleanup,
        change following:
          1) Avoid passing filenames between processes, pass fds
          2) When mmap'ing files, delete them immediately after
             opening and mmap'ing them.
          3) Pass sockets with fds during fork+exec instead of
             passing them via the filesystem.
          4) Use mmap'ed files for implementation of SharedMemory.
             QSharedMemory does not support cleanup correctly.

        Consquences:
          - Move MappedMemory to SharedMemory, make UpdateChunk use this.
          - Implement CoreIPC::Attachment using mmaped files.
          - Send messages using datagram socket. This solution works
            similiarly to Mach ports on Mac.
          - Send big messages out-of-line and thus avoid increasing
            the receive buffer.
          - Remove MemoryMappedPool and rely on libc/kernel caching
            of mmapped areas.
          - Unmap memory areas after use.
          - When UI process crashes, kill the web process using SIGKILL.
            This is possible again because cleanup handler is not needed.

        [WK2][Qt] Multiple problems with MemoryMappedPool
        https://bugs.webkit.org/show_bug.cgi?id=51984

        * Platform/CoreIPC/Attachment.cpp:
        (CoreIPC::Attachment::Attachment):
        * Platform/CoreIPC/Attachment.h:
        (CoreIPC::Attachment::size):
        (CoreIPC::Attachment::releaseFileDescriptor):
        (CoreIPC::Attachment::fileDescriptor):
        * Platform/CoreIPC/Connection.h:
        * Platform/CoreIPC/qt/ConnectionQt.cpp:
        (CoreIPC::MessageInfo::MessageInfo):
        (CoreIPC::MessageInfo::setMessageBodyOOL):
        (CoreIPC::MessageInfo::isMessageBodyOOL):
        (CoreIPC::MessageInfo::bodySize):
        (CoreIPC::MessageInfo::messageID):
        (CoreIPC::MessageInfo::attachmentCount):
        (CoreIPC::Connection::platformInitialize):
        (CoreIPC::Connection::platformInvalidate):
        (CoreIPC::SocketNotifierDisableGuard::SocketNotifierDisableGuard):
        (CoreIPC::SocketNotifierDisableGuard::~SocketNotifierDisableGuard):
        (CoreIPC::Connection::readyReadHandler):
        (CoreIPC::Connection::open):
        (CoreIPC::Connection::platformCanSendOutgoingMessages):
        (CoreIPC::Connection::sendOutgoingMessage):
        * Platform/SharedMemory.h:
        * Platform/WorkQueue.h:
        * Platform/qt/MappedMemoryPool.cpp: Removed.
        * Platform/qt/MappedMemoryPool.h: Removed.
        * Platform/qt/SharedMemoryQt.cpp:
        (WebKit::SharedMemory::Handle::Handle):
        (WebKit::SharedMemory::Handle::~Handle):
        (WebKit::SharedMemory::Handle::isNull):
        (WebKit::SharedMemory::Handle::encode):
        (WebKit::SharedMemory::Handle::decode):
        (WebKit::SharedMemory::Handle::releaseToAttachment):
        (WebKit::SharedMemory::Handle::adoptFromAttachment):
        (WebKit::SharedMemory::create):
        (WebKit::accessModeMMap):
        (WebKit::SharedMemory::~SharedMemory):
        (WebKit::accessModeFile):
        (WebKit::SharedMemory::createHandle):
        * Platform/qt/WorkQueueQt.cpp:
        (WorkQueue::registerSocketEventHandler):
        * Shared/qt/UpdateChunk.cpp:
        (WebKit::UpdateChunk::UpdateChunk):
        (WebKit::UpdateChunk::~UpdateChunk):
        (WebKit::UpdateChunk::encode):
        (WebKit::UpdateChunk::decode):
        (WebKit::UpdateChunk::createImage):
        * Shared/qt/UpdateChunk.h:
        * UIProcess/Launcher/ProcessLauncher.h:
        * UIProcess/Launcher/qt/ProcessLauncherQt.cpp:
        (WebKit::QtWebProcess::QtWebProcess):
        (WebKit::QtWebProcess::setupChildProcess):
        (WebKit::ProcessLauncher::launchProcess):
        (WebKit::ProcessLauncher::platformInvalidate):
        * UIProcess/Launcher/qt/ThreadLauncherQt.cpp:
        (WebKit::webThreadBody):
        (WebKit::ThreadLauncher::createWebThread):
        * WebKit2.pro:
        * WebProcess/qt/WebProcessMainQt.cpp:
        (WebKit::WebProcessMainQt):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@76507 268f45cc-cd09-0410-ab3c-d52691b4dbfc