Use failedAt in more places (misc)

pkg/compiler/lib/src/diagnostics/invariant.dart

 // 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.
 
 library dart2js.diagnostics.invariant;
 
 import 'spannable.dart';
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
 const bool REPORT_EXCESS_RESOLUTION = false;
 
 /// Flag that can be used in assertions to assert that a code path is only
 /// executed as part of development.
 ///
 /// This flag is automatically set to true if helper methods like, [debugPrint],
 /// [debugWrapPrint], [trace], and [reportHere] are called.
 bool DEBUG_MODE = false;
 
 /// Assert that [DEBUG_MODE] is `true` and provide [message] as part of the
 /// error message.
 assertDebugMode(String message) {
-  assert(invariant(NO_LOCATION_SPANNABLE, DEBUG_MODE,
-      message: 'Debug mode is not enabled: $message'));
+  assert(DEBUG_MODE,
+      failedAt(NO_LOCATION_SPANNABLE, 'Debug mode is not enabled: $message'));
 }
 
 /**
  * Throws a [SpannableAssertionFailure] if [condition] is
  * [:false:]. [condition] must be either a [:bool:] or a no-arg
  * function returning a [:bool:].
  *
  * Use this method to provide better information for assertion by calling
  * [invariant] as the argument to an [:assert:] statement:
  *
@@ skipping 43 matching lines @@
         'Spannable was null for failedInvariant. '
         'Use CURRENT_ELEMENT_SPANNABLE.');
   }
   if (message is Function) {
     message = message();
   }
   throw new SpannableAssertionFailure(spannable, message);
 }
 
 typedef void InternalErrorFunction(Spannable location, String message);