Merge r10809 from the bleeding_edge to the 3.8 branch.

src/platform-cygwin.cc

Index: src/platform-cygwin.cc
===================================================================
--- src/platform-cygwin.cc	(revision 10877)
+++ src/platform-cygwin.cc	(working copy)
@@ -355,6 +355,17 @@
 }
 
 
+bool VirtualMemory::Guard(void* address) {
+  if (NULL == VirtualAlloc(address,
+                           OS::CommitPageSize(),
+                           MEM_COMMIT,
+                           PAGE_READONLY | PAGE_GUARD)) {
+    return false;
+  }
+  return true;
+}
+
+
 class Thread::PlatformData : public Malloced {
  public:
   PlatformData() : thread_(kNoThread) {}