Remove factory body in *.fromEnvironment, and implement this same behavior

pkg/compiler/lib/src/resolution/members.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.resolution.members;
 
 import 'package:front_end/src/fasta/scanner.dart' show isUserDefinableOperator;
 
 import '../common.dart';
 import '../common/names.dart' show Selectors;
@@ skipping 3833 matching lines @@
     ConstructorResult result = resolveConstructor(node);
     ConstructorElement constructor = result.element;
     if (resolution.commonElements.isSymbolConstructor(constructor)) {
       registry.registerFeature(Feature.SYMBOL_CONSTRUCTOR);
     }
     ArgumentsResult argumentsResult;
     if (node.isConst) {
       argumentsResult =
           inConstantContext(() => resolveArguments(node.send.argumentsNode));
     } else {
+      if (!node.isConst && constructor.isFromEnvironmentConstructor) {
+        // TODO(sigmund): consider turning this into a compile-time-error.
+        reporter.reportHintMessage(
+            node,
+            MessageKind.FROM_ENVIRONMENT_MUST_BE_CONST,
+            {'className': constructor.enclosingClass.name});
+        registry.registerFeature(Feature.THROW_UNSUPPORTED_ERROR);
+      }
       argumentsResult = resolveArguments(node.send.argumentsNode);
     }
     // TODO(johnniwinther): Avoid the need for a [Selector].
     Selector selector = resolveSelector(node.send, constructor);
     CallStructure callStructure = selector.callStructure;
     registry.useElement(node.send, constructor);
 
     ResolutionDartType type = result.type;
     ConstructorAccessKind kind;
     bool isInvalid = false;
@@ skipping 939 matching lines @@
     }
     return const NoneResult();
   }
 }
 
 /// Looks up [name] in [scope] and unwraps the result.
 Element lookupInScope(
     DiagnosticReporter reporter, Node node, Scope scope, String name) {
   return Elements.unwrap(scope.lookup(name), reporter, node);
 }