Remove DeviceMonitorLinux::WillDestroyCurrentMessageLoop().

device/usb/usb_service.h

Index: device/usb/usb_service.h
diff --git a/device/usb/usb_service.h b/device/usb/usb_service.h
index 85a3922461ccaf5af507a81fb2053d4f9511d94f..99b626d030632b0e9ba880c02b2e4642a998d881 100644
--- a/device/usb/usb_service.h
+++ b/device/usb/usb_service.h
@@ -12,6 +12,7 @@
 #include <vector>
 
 #include "base/bind_helpers.h"
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
@@ -57,6 +58,11 @@ class UsbService : public base::NonThreadSafe {
 
   scoped_refptr<UsbDevice> GetDevice(const std::string& guid);
 
+  // Shuts down the UsbService. Must be called before destroying the UsbService
+  // when tasks can still be posted to the |blocking_task_runner| provided to
+  // Create().
+  virtual void Shutdown();
+
   // Enumerates available devices.
   virtual void GetDevices(const GetDevicesCallback& callback);
 
@@ -89,14 +95,16 @@ class UsbService : public base::NonThreadSafe {
   }
 
  private:
-  friend void base::DeletePointer<UsbService>(UsbService* service);
-
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
   scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
   std::unordered_map<std::string, scoped_refptr<UsbDevice>> devices_;
   std::unordered_set<std::string> testing_devices_;
   base::ObserverList<Observer, true> observer_list_;
 
+#if DCHECK_IS_ON()
+  bool did_shutdown_ = false;
+#endif
+
   DISALLOW_COPY_AND_ASSIGN(UsbService);
 };