Reviewed by Geoffrey Garen.

        Make malloc validation useful
        https://bugs.webkit.org/show_bug.cgi?id=57502

        This patch changes FAST_MALLOC_MATCH_VALIDATION with a general
        corruption check that tags the beginning and end of all allocations
        to check for write overflows and overwrites the contents of
        memory on free in order to (hopefully) show up use-after-free issues
        sooner.

        We also turn it on by default for debug builds.

        * JavaScriptCore.exp:
        * wtf/FastMalloc.cpp:
        (WTF::tryFastMalloc):
        (WTF::fastMalloc):
        (WTF::tryFastCalloc):
        (WTF::fastCalloc):
        (WTF::fastFree):
        (WTF::tryFastRealloc):
        (WTF::fastRealloc):
        (WTF::TCMalloc_PageHeap::isScavengerSuspended):
        (WTF::TCMalloc_PageHeap::scheduleScavenger):
        (WTF::TCMalloc_PageHeap::suspendScavenger):
        (WTF::TCMalloc_PageHeap::signalScavenger):
        (WTF::TCMallocStats::malloc):
        (WTF::TCMallocStats::free):
        (WTF::TCMallocStats::fastCalloc):
        (WTF::TCMallocStats::tryFastCalloc):
        (WTF::TCMallocStats::calloc):
        (WTF::TCMallocStats::fastRealloc):
        (WTF::TCMallocStats::tryFastRealloc):
        (WTF::TCMallocStats::realloc):
        * wtf/FastMalloc.h:
        (WTF::Internal::fastMallocValidationHeader):
        (WTF::Internal::fastMallocValidationSuffix):
        (WTF::Internal::fastMallocMatchValidationType):
        (WTF::Internal::setFastMallocMatchValidationType):
        (WTF::fastMallocMatchValidateFree):
        (WTF::fastMallocValidate):
        * wtf/Platform.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@82876 268f45cc-cd09-0410-ab3c-d52691b4dbfc