Add HidConnection::Close and register OS X callbacks on the UI thread.

The platform implementation of a HID connection may need to cancel I/O
operations when the connection is closed. If this is done during the
object destructor then any pointers held by those pending operations are
immediately invalid. A separate Close method allows the cleanup to
happen while the object is still available to handle asynchronous
cancellation events.

The OS X implementation will take advantage of this immediately to
register and unregister its input report callback from the UI thread to
avoid a race between event delivery and object cleanup. I've added
comments explaining why not all operations on the IOHIDDevice object
could be moved to the UI thread.

BUG=418207

Review URL: https://codereview.chromium.org/615633008

Cr-Commit-Position: refs/heads/master@{#298384}

1 files changed, 3 insertions, 0 deletions

diff --git a/device/hid/hid_connection_win.cc b/device/hid/hid_connection_win.cc
index 4f39c7c..a8414da 100644
--- a/device/hid/hid_connection_win.cc
+++ b/device/hid/hid_connection_win.cc
@@ -125,6 +125,9 @@ HidConnectionWin::HidConnectionWin(const HidDeviceInfo& device_info)
 }
 
 HidConnectionWin::~HidConnectionWin() {
+}
+
+void HidConnectionWin::PlatformClose() {
   CancelIo(file_.Get());
 }