Privatize StrongBinding lifetime management

device/usb/mojo/device_impl_unittest.cc

Index: device/usb/mojo/device_impl_unittest.cc
diff --git a/device/usb/mojo/device_impl_unittest.cc b/device/usb/mojo/device_impl_unittest.cc
index 9617d0267520bfb18bbaa825f382873591c336f3..5bb40e6e23a0effd29afaacfa6cc61b75405b89a 100644
--- a/device/usb/mojo/device_impl_unittest.cc
+++ b/device/usb/mojo/device_impl_unittest.cc
@@ -26,6 +26,7 @@
 #include "device/usb/mojo/mock_permission_provider.h"
 #include "device/usb/mojo/type_converters.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
+#include "mojo/public/cpp/bindings/strong_binding.h"
 #include "net/base/io_buffer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -175,6 +176,8 @@ class USBDeviceImplTest : public testing::Test {
     mock_handle_ = new MockUsbDeviceHandle(mock_device_.get());
 
     DevicePtr proxy;
+
+    // Owns itself.
     new DeviceImpl(
         mock_device_,
         DeviceInfo::From(static_cast<const UsbDevice&>(*mock_device_)),