Open IOHIDDevices on the FILE thread

device/hid/hid_service_mac.h

Index: device/hid/hid_service_mac.h
diff --git a/device/hid/hid_service_mac.h b/device/hid/hid_service_mac.h
index f3af539a25205614166df8a0ced2794ad7f3be31..2d2ac3513997948a83101ccb69c0ca1b46f4464c 100644
--- a/device/hid/hid_service_mac.h
+++ b/device/hid/hid_service_mac.h
@@ -7,6 +7,7 @@
 
 #include <CoreFoundation/CoreFoundation.h>
 #include <IOKit/IOKitLib.h>
+#include <IOKit/hid/IOHIDDevice.h>
 
 #include <string>
 
@@ -15,6 +16,7 @@
 #include "base/mac/scoped_ioobject.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "device/hid/hid_service.h"
 
 namespace base {
@@ -32,6 +34,15 @@ class HidServiceMac : public HidService {
                const ConnectCallback& connect) override;
 
  private:
+  static void OpenOnBlockingThread(
+      scoped_refptr<HidDeviceInfo> device_info,
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+      base::WeakPtr<HidServiceMac> hid_service,
+      const ConnectCallback& callback);
+  void DeviceOpened(scoped_refptr<HidDeviceInfo> device_info,
+                    base::ScopedCFTypeRef<IOHIDDeviceRef> hid_device,
+                    const ConnectCallback& callback);
+
   // IOService matching callbacks.
   static void FirstMatchCallback(void* context, io_iterator_t iterator);
   static void TerminatedCallback(void* context, io_iterator_t iterator);
@@ -54,6 +65,8 @@ class HidServiceMac : public HidService {
   // on which slow running I/O operations can be performed.
   scoped_refptr<base::SingleThreadTaskRunner> file_task_runner_;
 
+  base::WeakPtrFactory<HidServiceMac> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(HidServiceMac);
 };