Disable Quarantine tests on platforms its not supported.

content/common/quarantine/quarantine_linux.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/public/common/quarantine.h"
 
 #include <stddef.h>
 #include <sys/types.h>
 #include <sys/xattr.h>
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
+#include "base/files/scoped_temp_dir.h"
 #include "base/logging.h"
 #include "base/threading/thread_restrictions.h"
 #include "content/common/quarantine/quarantine_constants_linux.h"
 #include "url/gurl.h"
 
 namespace content {
 
 const char kSourceURLExtendedAttrName[] = "user.xdg.origin.url";
 const char kReferrerURLExtendedAttrName[] = "user.xdg.referrer.url";
 
@@ skipping 66 matching lines @@
 
   if (source_url != GURL(url_value))
     return false;
 
   return !referrer_url.is_valid() ||
          GURL(GetExtendedFileAttribute(file.value().c_str(),
                                        kReferrerURLExtendedAttrName)) ==
              referrer_url;
 }
 
+// Only to be used in tests.
+bool IsQuarantineSupportedForTesting() {

[bcf, 2017/01/06 20:43:00]

We should update quarantine_linux_unittest.cc to use this new function in
QuarantineLinuxTest::SetUp

+    base::ScopedTempDir temp_dir;
+    if (!temp_dir.CreateUniqueTempDir())
+      return false;
+
+    base::FilePath xattr_test_file;
+    if (!base::CreateTemporaryFileInDir(temp_dir.GetPath(), &xattr_test_file))
+      return false;
+
+    int result =
+        setxattr(xattr_test_file.value().c_str(), "user.test", "test", 4, 0);
+    bool is_xattr_supported = (!result) || (errno != ENOTSUP);
+
+    return is_xattr_supported;
+}
+
 }  // namespace content