After performing scavenge, hint OS that data in from spaces are no more neede...

src/platform-win32.cc

Index: src/platform-win32.cc
===================================================================
--- src/platform-win32.cc	(revision 3342)
+++ src/platform-win32.cc	(working copy)
@@ -1377,6 +1377,12 @@
 }
 
 
+bool VirtualMemory::Reset(void* address, size_t size, bool is_executable) {
+  int prot = is_executable ? PAGE_EXECUTE_READWRITE : PAGE_READWRITE;
+  return NULL != VirtualAlloc(address, size, MEM_RESET, PAGE_READWRITE);
+}
+
+
 // ----------------------------------------------------------------------------
 // Win32 thread support.