Emit a compile-time error when a named optional parameter has a library private name.

tests/co19/co19-dart2js.status

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 [ $compiler == dart2js && $runtime == jsshell ]
 LibTest/isolate/isolate_api/spawnUri_A02_t01: Crash # TODO(ahe): Please triage this crash.
 LibTest/core/List/sort_A01_t04: Fail, Pass, Timeout # Must be a bug in jsshell, test sometimes times out.
 
 [ $compiler == dart2js && $checked && $runtime == ie9 ]
 LibTest/core/Uri/encodeQueryComponent_A01_t02: Pass, Timeout # co19-roll r576: Please triage this failure
@@ skipping 292 matching lines @@
 LibTest/math/log_A01_t01: Fail # TODO(kasperl): Please triage.
 
 
 [ $compiler == dart2js && ($runtime == ie10 || $runtime == ff || $runtime == chrome || $runtime == drt || $runtime == safari || $runtime == opera) ]
 *: Skip
 
 #
 # Missing compile-time errors.
 #
 [ $compiler == dart2js ]
-Language/06_Functions/2_Formal_Parameters/2_Optional_Formals_A03_t03: MissingCompileTimeError # TODO(ahe): Enforce optional parameter semantics.
-Language/06_Functions/2_Formal_Parameters/2_Optional_Formals_A03_t04: MissingCompileTimeError # TODO(ahe): Enforce optional parameter semantics.
 Language/07_Classes/07_Classes_A02_t11: MissingCompileTimeError # Checks that it is a compile-time error if a static final variable declaration does not include explicit initializer.
 Language/12_Expressions/01_Constants_A20_t03: MissingCompileTimeError # Checks that an identifier expression that denotes a type parameter  can not be assigned to a constant variable.
 Language/12_Expressions/05_Strings/1_String_Interpolation_A01_t09: MissingCompileTimeError # Checks that it is a compile-time error if a string interpolation construct does not start with IDENTIFIER_NO_DOLLAR or opening brace.
 Language/12_Expressions/05_Strings_A02_t46: MissingCompileTimeError # Checks that multi-line strings that contain characters and sequences prohibited by this grammar, cause compile-time errors.
 Language/12_Expressions/05_Strings_A02_t48: MissingCompileTimeError # Checks that multi-line strings that contain characters and sequences prohibited by this grammar, cause compile-time errors.
 Language/12_Expressions/30_Identifier_Reference_A04_t09: MissingCompileTimeError # Checks that it is a compile-time error when a built-in identifier dynamic is used as the declared name of a type variable.
 Language/12_Expressions/30_Identifier_Reference_A05_t01: MissingCompileTimeError # Checks that it is a compile-time error when a built-in identifier "abstract" is used as a type annotation of a local variable.
 Language/12_Expressions/30_Identifier_Reference_A05_t12: MissingCompileTimeError # Checks that it is a compile-time error when a built-in identifier "static" is used as a type annotation of a local variable.
 Language/16_Reference/1_Lexical_Rules/1_Reserved_Words_A40_t04: MissingCompileTimeError # Checks that other Unicode whitespaces are not allowed:  check NO-BREAK SPACE (U+00A0)
 Language/16_Reference/1_Lexical_Rules_A02_t06: MissingCompileTimeError # Checks that Unicode whitespaces other than WHITESPACE are not permitted in the source code. Checks symbol U+00a0.
@@ skipping 305 matching lines @@
 
 [ $compiler == dart2js ]
 Language/07_Classes/6_Constructors/3_Constant_Constructors_A05_t04: fail # co19-roll r587: Please triage this failure
 Language/07_Classes/6_Constructors/3_Constant_Constructors_A05_t04: fail # co19-roll r587: Please triage this failure
 LibTest/json/stringify_A01_t01: fail # co19-roll r587: Please triage this failure
 LibTest/json/stringify_A02_t01: fail # co19-roll r587: Please triage this failure
 LibTest/math/pow_A04_t01: fail # co19-roll r587: Please triage this failure
 LibTest/math/pow_A14_t01: fail # co19-roll r587: Please triage this failure
 LibTest/math/pow_A16_t01: fail # co19-roll r587: Please triage this failure