In Linux Port, make a dummy HOME directory for running tests.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux_unittest.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux_unittest.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux_unittest.py b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux_unittest.py
index 1f802d822743f20e9ff6b5f18b5b65922e8ba8cd..6825a8b2bd7e4a0d5320b169bfaf1e9c2159ffbe 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux_unittest.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux_unittest.py
@@ -26,13 +26,13 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+import os
 
 from webkitpy.common.system import executive_mock
 from webkitpy.common.system.systemhost_mock import MockSystemHost
-from webkitpy.tool.mock_tool import MockOptions
-
 from webkitpy.layout_tests.port import linux
 from webkitpy.layout_tests.port import port_testcase
+from webkitpy.tool.mock_tool import MockOptions
 
 
 class LinuxPortTest(port_testcase.PortTestCase):
@@ -42,6 +42,13 @@ class LinuxPortTest(port_testcase.PortTestCase):
     full_port_name = 'linux-trusty'
     port_maker = linux.LinuxPort
 
+    def setUp(self):
+        # TODO(qyearsley): Remove this when crbug.com/627887 is fixed.
+        self.original_environ = os.environ.copy()
+
+    def tearDown(self):
+        os.environ = self.original_environ
+
     def assert_version_properties(self, port_name, os_version, expected_name,
                                   expected_version,
                                   driver_file_output=None):
@@ -101,3 +108,17 @@ class LinuxPortTest(port_testcase.PortTestCase):
 
     def test_path_to_image_diff(self):
         self.assertEqual(self.make_port()._path_to_image_diff(), '/mock-checkout/out/Release/image_diff')
+
+    def test_dummy_home_dir(self):
+        original_home = '/home/user'
+        os.environ['HOME'] = original_home
+        port = self.make_port()
+        # Set up the test run; the temporary home directory should be set up.
+        port.setup_test_run()
+        temp_home_dir = os.environ['HOME']
+        self.assertNotEqual(temp_home_dir, original_home)
+        self.assertTrue(port._filesystem.isdir(temp_home_dir))
+        # Clean up; HOME should be reset and the temp dir should be cleaned up.
+        port.clean_up_test_run()
+        self.assertEqual(os.environ.get('HOME'), original_home)
+        self.assertFalse(port._filesystem.exists(temp_home_dir))