fixup! [ozone/wayland] Add clipboard support

This CL is a fixup of [1] and also reverts [2], making
all ozone_unittests run on linux.chromeos bots, without any skips,
for both xdg_v5 and xdg_v6 shell implementations.

Basically, CL brings some important code out of DCHECK. It was
not affecting me locally, because I either build with is_debug
or dcheck_always_on.

[1] https://crrev.com/c/976461
[2] https://crrev.com/c/1027030

R=rjkroege@chromium.org
TEST=ozone_unittests

BUG=578890

Change-Id: I18092d09df85e7aa78b85d208ba372504cd8ede9
Reviewed-on: https://chromium-review.googlesource.com/1028030Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/master@{#553650}

ui/ozone/platform/wayland/wayland_data_device_unittest.cc

@@ -131,12 +131,10 @@ TEST_P(WaylandDataDeviceManagerTest, IsSelectionOwner) {
   ASSERT_FALSE(clipboard_client_->IsSelectionOwner());
 }
 
-// TODO(tonikitoo): Deliberately skip running these specific unittests on
-// XDG_v5. ChromeOS/Linux builder running on 14.04, which seems to have a
-// mis-functioning XDG v5 implementation.
-//
-// Details:
-// https://ci.chromium.org/buildbot/chromium.chromiumos/linux-chromeos-rel/7224
+INSTANTIATE_TEST_CASE_P(XdgVersionV5Test,
+                        WaylandDataDeviceManagerTest,
+                        ::testing::Values(kXdgShellV5));
+
 INSTANTIATE_TEST_CASE_P(XdgVersionV6Test,
                         WaylandDataDeviceManagerTest,
                         ::testing::Values(kXdgShellV6));

ui/ozone/platform/wayland/wayland_data_source.cc

@@ -58,7 +58,9 @@ void WaylandDataSource::OnSend(void* data,
     self->GetClipboardData("text/plain", &mime_data);
 
   std::string contents(mime_data->begin(), mime_data->end());
-  DCHECK(base::WriteFileDescriptor(fd, contents.data(), contents.length()));
+  bool result =
+      base::WriteFileDescriptor(fd, contents.data(), contents.length());
+  DCHECK(result);
   close(fd);
 }