Add --trace_type_check_elimination flag for debugging purposes.

runtime/vm/class_finalizer.cc

 // 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.
 
 #include "vm/class_finalizer.h"
 
 #include "vm/flags.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
 #include "vm/longjump.h"
@@ skipping 143 matching lines @@
         class_function = test_class.LookupDynamicFunction(function_name);
       }
       if (class_function.IsNull()) {
         OS::PrintErr("%s implements '%s' missing: '%s'\n",
                      class_name.ToCString(),
                      interface_name.ToCString(),
                      function_name.ToCString());
       } else {
         Error& malformed_error = Error::Handle();
         if (!class_function.IsSubtypeOf(TypeArguments::Handle(),
-                                             interface_function,
-                                             TypeArguments::Handle(),
-                                             &malformed_error)) {
+                                        interface_function,
+                                        TypeArguments::Handle(),
+                                        &malformed_error)) {
           if (!malformed_error.IsNull()) {
             OS::PrintErr("%s\n", malformed_error.ToErrorCString());
           }
           OS::PrintErr("The type of instance method '%s' in class '%s' is not "
                        "a subtype of the type of '%s' in interface '%s'\n",
                        function_name.ToCString(),
                        class_name.ToCString(),
                        function_name.ToCString(),
                        interface_name.ToCString());
         }
@@ skipping 1320 matching lines @@
 void ClassFinalizer::ReportError(const char* format, ...) {
   va_list args;
   va_start(args, format);
   const Error& error = Error::Handle(
       Parser::FormatError(Script::Handle(), -1, "Error", format, args));
   va_end(args);
   ReportError(error);
 }
 
 }  // namespace dart