Do not pass tautology predicates into check list.

lib/html/scripts/systemhtml.py

Index: lib/html/scripts/systemhtml.py
diff --git a/lib/html/scripts/systemhtml.py b/lib/html/scripts/systemhtml.py
index dd776674c531d9dbacbe9731e2ca9945cc050d98..44553c421cc54213e73ba3e48cf7fc9eb6de8906 100644
--- a/lib/html/scripts/systemhtml.py
+++ b/lib/html/scripts/systemhtml.py
@@ -915,7 +915,6 @@ class Dart2JSBackend(object):
     temp_version = [0]
 
     def GenerateCall(operation, argument_count, checks):
-      checks = filter(lambda e: e != 'true', checks)
       if checks:
         (stmts_emitter, call_emitter) = body.Emit(
             '    if ($CHECKS) {\n$!STMTS$!CALL    }\n',
@@ -981,18 +980,17 @@ class Dart2JSBackend(object):
           NATIVE=info.declared_name)
 
     def GenerateChecksAndCall(operation, argument_count):
-      checks = ['!?%s' % name for name in parameter_names]
+      checks = []
       for i in range(0, argument_count):
         argument = operation.arguments[i]
         parameter_name = parameter_names[i]
         test_type = self._DartType(argument.type.id)
         if test_type in ['dynamic', 'Object']:
-          checks[i] = '?%s' % parameter_name
-        elif test_type == parameter_types[i]:
-          checks[i] = 'true'
-        else:
-          checks[i] = '(%s is %s || %s == null)' % (
-              parameter_name, test_type, parameter_name)
+          checks.append('?%s' % parameter_name)
+        elif test_type != parameter_types[i]:
+          checks.append('(%s is %s || %s == null)' % (
+              parameter_name, test_type, parameter_name))
+      checks.extend(['!?%s' % name for name in parameter_names[argument_count:]])
       # There can be multiple presence checks.  We need them all since a later
       # optional argument could have been passed by name, leaving 'holes'.
       GenerateCall(operation, argument_count, checks)