Fix compilation error on Fedora 20.

The libudev commit below changed the return types of _undef functions
from void to the matching the argument type, e.g. void udev_unref(udev*)
became udev* udev_unref(udev*).
http://cgit.freedesktop.org/systemd/systemd/commit/?id=20bbd54f603994a3cc211d2795de16550882ed8d

This change adds a bit of template magic to make Chromium compile with
either version of the libudev headers.

BUG=340108
TEST=ninja -C out/Debug chrome

Review URL: https://codereview.chromium.org/138783005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248447 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 16 insertions, 4 deletions

diff --git a/device/hid/hid_service_linux.h b/device/hid/hid_service_linux.h
index 415db80..ba58fad 100644
--- a/device/hid/hid_service_linux.h
+++ b/device/hid/hid_service_linux.h
@@ -18,6 +18,11 @@ namespace device {
 class HidConnection;
 
 template<typename T, void func(T*)>
+void DiscardReturnType(T* arg) { func(arg); }
+template<typename T, T* func(T*)>
+void DiscardReturnType(T* arg) { func(arg); }
+
+template<typename T, void func(T*)>
 struct Deleter {
   void operator()(T* enumerate) const {
     if (enumerate != NULL)
@@ -25,10 +30,17 @@ struct Deleter {
   }
 };
 
-typedef Deleter<udev_enumerate, udev_enumerate_unref> UdevEnumerateDeleter;
-typedef Deleter<udev_device, udev_device_unref> UdevDeviceDeleter;
-typedef Deleter<udev, udev_unref> UdevDeleter;
-typedef Deleter<udev_monitor, udev_monitor_unref> UdevMonitorDeleter;
+typedef Deleter<
+    udev_enumerate,
+    DiscardReturnType<udev_enumerate, udev_enumerate_unref> >
+    UdevEnumerateDeleter;
+typedef Deleter<
+    udev_device,
+    DiscardReturnType<udev_device, udev_device_unref> > UdevDeviceDeleter;
+typedef Deleter<udev, DiscardReturnType<udev, udev_unref> > UdevDeleter;
+typedef Deleter<
+    udev_monitor,
+    DiscardReturnType<udev_monitor, udev_monitor_unref> > UdevMonitorDeleter;
 
 typedef scoped_ptr<udev_device, UdevDeviceDeleter> ScopedUdevDevicePtr;
 typedef scoped_ptr<udev_enumerate, UdevEnumerateDeleter> ScopedUdevEnumeratePtr;