PartitionAlloc: add a discardSystemPages() hint API.

Source/wtf/PageAllocator.cpp

Index: Source/wtf/PageAllocator.cpp
diff --git a/Source/wtf/PageAllocator.cpp b/Source/wtf/PageAllocator.cpp
index b9f3eae6a5c5bee8c75891eed51485995a55fc77..c257d991ffabb5994693c06d2d2049b7e6b58793 100644
--- a/Source/wtf/PageAllocator.cpp
+++ b/Source/wtf/PageAllocator.cpp
@@ -221,5 +221,17 @@ void recommitSystemPages(void* addr, size_t len)
 #endif
 }
 
+void discardSystemPages(void* addr, size_t len)
+{

[haraken, 2015/06/18 18:15:39]

Shall we add ASSERT(!(len & kSystemPageOffsetMask)) ?

+#if OS(POSIX)
+    decommitSystemPages(addr, len);
+#else
+    (void) addr;
+    (void) len;
+    // TODO(cevans): implement this using MEM_RESET for Windows, once we've
+    // decided that the semantics are a match.
+#endif
+}
+
 } // namespace WTF