Prepration for returning memory to the OS on Windows. Track whether a portion of a span of memory was returned to the OS.
If it was, ask that it be recommitted before returning it to the application as an allocated region.
Reviewed by Oliver Hunt.
(WTF::TCMalloc_PageHeap::New): If the span was decommitted, ask that it be recommitted before returning it.
(WTF::TCMalloc_PageHeap::AllocLarge): Ditto.
(WTF::TCMalloc_PageHeap::Carve): When splitting a span, ensure that the decommitted state propogates to the two new spans.
(WTF::TCMalloc_PageHeap::Delete): When merging a span, ensure that the resulting span is marked as decommitted if any of the
spans being merged were marked as decommitted.
(WTF::TCMalloc_PageHeap::IncrementalScavenge): Mark as decommitted after releasing the span.
(WTF::TCMalloc_Central_FreeList::FetchFromSpans): Add an assertion to catch a decommitted span being returned to the application
without first being recommitted.
(WTF::TCMalloc_Central_FreeList::Populate): Ditto.
- wtf/TCSystemAlloc.cpp: Stub out TCMalloc_SystemCommit.
- wtf/TCSystemAlloc.h: