Make the message test suite run without slow asserts.

test/message/testcfg.py

Index: test/message/testcfg.py
diff --git a/test/message/testcfg.py b/test/message/testcfg.py
index 411f71ceb2be179e25e8e8f0bffc4aad30debbc5..e4f3f5587a489f57058f0e5eaf7afc087a2e72c0 100644
--- a/test/message/testcfg.py
+++ b/test/message/testcfg.py
@@ -35,6 +35,7 @@ from testrunner.objects import testcase
 
 
 FLAGS_PATTERN = re.compile(r"//\s+Flags:(.*)")
+INVALID_FLAGS = ["--enable-slow-asserts"]
 
 
 class MessageTestSuite(testsuite.TestSuite):
@@ -62,6 +63,7 @@ class MessageTestSuite(testsuite.TestSuite):
     for match in flags_match:
       result += match.strip().split()
     result += context.mode_flags
+    result = [x for x in result if x not in INVALID_FLAGS]
     result.append(os.path.join(self.root, testcase.path + ".js"))
     return testcase.flags + result