Ensure mjsunit tests use dashes not underscores in flags directives.

tools/presubmit.py

Index: tools/presubmit.py
diff --git a/tools/presubmit.py b/tools/presubmit.py
index 32ad334a0aec8e5a7938e4298aaf88b78be0753e..a835e61792caad2f6858412c2263e0ce78fc2877 100755
--- a/tools/presubmit.py
+++ b/tools/presubmit.py
@@ -103,7 +103,7 @@ whitespace/todo
 # TODO(bmeurer): Fix and re-enable readability/check
 
 LINT_OUTPUT_PATTERN = re.compile(r'^.+[:(]\d+[:)]|^Done processing')
-
+FLAGS_LINE = re.compile("//\s*Flags:.*--([A-z0-9-])+_[A-z0-9].*\n")
 
 def CppLintWorker(command):
   try:
@@ -414,6 +414,12 @@ class SourceProcessor(SourceFileProcessor):
           print "%s does not have two empty lines between declarations " \
                 "in line %s." % (name, linenumbers)
         result = False
+    # Sanitize flags for fuzzer.
+    if "mjsunit" in name:
+      match = FLAGS_LINE.search(contents)
+      if match:
+        print "%s Flags should use '-' (not '_')" % name
+        result = False
     return result
 
   def ProcessFiles(self, files, path):