Make testing i18n the default.

tools/run-tests.py

Index: tools/run-tests.py
diff --git a/tools/run-tests.py b/tools/run-tests.py
index 48682d4444e586c8b48b1c146898b0dc17468ba8..c19f0a6849b27f9ede92a30f48d67b868ffe30ef 100755
--- a/tools/run-tests.py
+++ b/tools/run-tests.py
@@ -105,6 +105,8 @@ def BuildOptions():
   result.add_option("--extra-flags",
                     help="Additional flags to pass to each test command",
                     default="")
+  result.add_option("--i18n", help="Whether to test internationalization",
+                    default=False, action="store_true")
   result.add_option("--isolates", help="Whether to test isolates",
                     default=False, action="store_true")
   result.add_option("-j", help="The number of parallel tasks to run",
@@ -210,6 +212,8 @@ def ProcessOptions(options):
   if not options.flaky_tests in ["run", "skip", "dontcare"]:
     print "Unknown flaky test mode %s" % options.flaky_tests
     return False
+  if options.i18n:
+    DEFAULT_TESTS.append("intl")
   return True