Move constant systems into their own libraries.

pkg/compiler/lib/src/dart2jslib.dart

Index: pkg/compiler/lib/src/dart2jslib.dart
diff --git a/pkg/compiler/lib/src/dart2jslib.dart b/pkg/compiler/lib/src/dart2jslib.dart
index 2491ebcd1372e86c89af94e2054a78b8d3be6a5f..51a22ee0985fc403b0c2c652f3e3968b8c184e76 100644
--- a/pkg/compiler/lib/src/dart2jslib.dart
+++ b/pkg/compiler/lib/src/dart2jslib.dart
@@ -12,6 +12,9 @@ import 'dart:profiler' show
 import '../compiler.dart' as api;
 import 'cache_strategy.dart';
 import 'closure.dart' as closureMapping;
+import 'compile_time_constants.dart';
+import 'constant_system_dart.dart';
+import 'constants/constant_system.dart';
 import 'constants/expressions.dart';
 import 'constants/values.dart';
 import 'core_types.dart';
@@ -74,10 +77,7 @@ export 'util/util.dart'
          CURRENT_ELEMENT_SPANNABLE,
          NO_LOCATION_SPANNABLE;
 
-part 'compile_time_constants.dart';
 part 'compiler.dart';
-part 'constant_system.dart';
-part 'constant_system_dart.dart';
 part 'diagnostic_listener.dart';
 part 'enqueue.dart';
 part 'resolved_visitor.dart';