make gc branch compile on Win32.

src/platform-win32.cc

Index: src/platform-win32.cc
diff --git a/src/platform-win32.cc b/src/platform-win32.cc
index b5a85f6689fadbe961efff0ca30d62dbfdd6d896..1eb83432236c632e10dab1052d40ea5869380f2d 100644
--- a/src/platform-win32.cc
+++ b/src/platform-win32.cc
@@ -1416,6 +1416,33 @@ bool VirtualMemory::Uncommit(void* address, size_t size) {
 }
 
 
+void* VirtualMemory::ReserveRegion(size_t size) {
+  return VirtualAlloc(NULL, size, MEM_RESERVE, PAGE_NOACCESS);
+}
+
+
+bool VirtualMemory::CommitRegion(void* base, size_t size, bool is_executable) {
+  int prot = is_executable ? PAGE_EXECUTE_READWRITE : PAGE_READWRITE;
+  if (NULL == VirtualAlloc(base, size, MEM_COMMIT, prot)) {
+    return false;
+  }
+
+  UpdateAllocatedSpaceLimits(base, static_cast<int>(size));
+  return true;
+}
+
+
+bool VirtualMemory::UncommitRegion(void* base, size_t size) {
+  return VirtualFree(base, size, MEM_DECOMMIT) != false;
+}
+
+
+bool VirtualMemory::ReleaseRegion(void* base, size_t size) {
+  return VirtualFree(base, size, MEM_DECOMMIT) != false;
+}
+
+
+
 // ----------------------------------------------------------------------------
 // Win32 thread support.