Replace handles that the handle closer closes with dummy Events.

sandbox/win/src/handle_closer_agent.cc

Index: sandbox/win/src/handle_closer_agent.cc
diff --git a/sandbox/win/src/handle_closer_agent.cc b/sandbox/win/src/handle_closer_agent.cc
index 07c6a09854d2d5355a84f30f782ec57f1a04f3ab..1fa82553bb05c4677903702162a43e01e1ff2529 100644
--- a/sandbox/win/src/handle_closer_agent.cc
+++ b/sandbox/win/src/handle_closer_agent.cc
@@ -41,6 +41,50 @@ bool HandleCloserAgent::NeedsHandlesClosed() {
   return g_handles_to_close != NULL;
 }
 
+HandleCloserAgent::HandleCloserAgent()
+    : dummy_handle_(::CreateEvent(NULL, FALSE, FALSE, NULL)) {
+}
+
+// Attempts to stuff |closed_handle| with a duplicated handle for a dummy Event
+// with no access. This should allow the handle to be closed, to avoid
+// generating EXCEPTION_INVALID_HANDLE on shutdown, but nothing else. For now
+// the only supported |type| is Event or File.
+bool HandleCloserAgent::AttemptToStuffHandleSlot(HANDLE closed_handle,
+                                                 const base::string16& type) {
+  // Only attempt to stuff Files and Events at the moment.
+  if (type != L"Event" && type != L"File") {
+    return true;
+  }
+
+  if (!dummy_handle_.IsValid())
+    return false;
+
+  // This should never happen, as g_dummy is created before closing to_stuff.
+  DCHECK(dummy_handle_.Get() != closed_handle);
+
+  std::vector<HANDLE> to_close;
+  HANDLE dup_dummy = NULL;
+  size_t count = 16;
+
+  do {
+    if (!::DuplicateHandle(::GetCurrentProcess(), dummy_handle_.Get(),
+                           ::GetCurrentProcess(), &dup_dummy, 0, FALSE, 0))
+      break;
+    if (dup_dummy != closed_handle)
+      to_close.push_back(dup_dummy);
+  } while (count-- &&
+           reinterpret_cast<uintptr_t>(dup_dummy) <
+               reinterpret_cast<uintptr_t>(closed_handle));
+
+  for (auto h : to_close)
+    ::CloseHandle(h);
+
+  // Useful to know when we're not able to stuff handles.
+  DCHECK(dup_dummy == closed_handle);
+
+  return dup_dummy == closed_handle;
+}
+
 // Reads g_handles_to_close and creates the lookup map.
 void HandleCloserAgent::InitializeHandlesToClose() {
   CHECK(g_handles_to_close != NULL);
@@ -136,6 +180,8 @@ bool HandleCloserAgent::CloseHandles() {
         return false;
       if (!::CloseHandle(handle))
         return false;
+      // Attempt to stuff this handle with a new dummy Event.
+      AttemptToStuffHandleSlot(handle, result->first);
     }
   }