auto merge of #5210 : GreenRecycleBin/servo/#4968, r=jdm

`./mach test tests/wpt/web-platform-tests/html/browsers/history/the-location-interface/security_location_0.sub.htm` is still failing with the same message as reported in #3219.

python/servo/command_base.py

@@ -120,7 +120,7 @@ class CommandBase(object):
             self._cargo_build_id = open(filename).read().strip()
         return self._cargo_build_id
 
-    def build_env(self, gonk=False):
+    def build_env(self, gonk=False, hosts_file_path=None):
         """Return an extended environment dictionary."""
         env = os.environ.copy()
         extra_path = []
@@ -206,6 +206,9 @@ class CommandBase(object):
         if "ANDROID_TOOLCHAIN" in env:
             env["NDK_STANDALONE"] = env["ANDROID_TOOLCHAIN"]
 
+        if hosts_file_path:
+            env['HOST_FILE'] = hosts_file_path
+
         return env
 
     def servo_crate(self):

python/servo/testing_commands.py

@@ -30,8 +30,8 @@ class MachCommands(CommandBase):
         if self.context.built_tests:
             return
         returncode = Registrar.dispatch('build-tests', context=self.context)
-	if returncode:
-	    sys.exit(returncode)
+        if returncode:
+            sys.exit(returncode)
         self.context.built_tests = True
 
     def find_test(self, prefix):
@@ -238,7 +238,8 @@ class MachCommands(CommandBase):
 
         processes = str(multiprocessing.cpu_count()) if processes is None else processes
         params = params + ["--processes", processes]
+        hosts_file_path = path.join('tests', 'wpt', 'hosts')
 
         return subprocess.call(
             ["bash", path.join("tests", "wpt", "run.sh")] + params,
-            env=self.build_env())
+            env=self.build_env(hosts_file_path=hosts_file_path))