Mark empty HashMap constructor as NoThrows.

sdk/lib/_internal/compiler/js_lib/collection_patch.dart

 // Copyright (c) 2013, 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.
 
 // Patch file for dart:collection classes.
 import 'dart:_foreign_helper' show JS;
-import 'dart:_js_helper' show fillLiteralMap, NoInline, patch;
+import 'dart:_js_helper' show fillLiteralMap, NoInline, NoThrows, patch;
 
 @patch
 class HashMap<K, V> {
   @patch
   factory HashMap({ bool equals(K key1, K key2),
                     int hashCode(K key),
                     bool isValidKey(potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
@@ skipping 498 matching lines @@
   @patch
   factory LinkedHashMap.identity() = _LinkedIdentityHashMap<K, V>;
 
   // Private factory constructor called by generated code for map literals.
   @NoInline()
   factory LinkedHashMap._literal(List keyValuePairs) {
     return fillLiteralMap(keyValuePairs, new _LinkedHashMap<K, V>());
   }
 
   // Private factory constructor called by generated code for map literals.
-  @NoInline()
+  @NoThrows() @NoInline()
   factory LinkedHashMap._empty() {
     return new _LinkedHashMap<K, V>();
   }
 }
 
 class _LinkedHashMap<K, V> implements LinkedHashMap<K, V> {
   int _length = 0;
 
   // The hash map contents are divided into three parts: one part for
   // string keys, one for numeric keys, and one for the rest. String
@@ skipping 1291 matching lines @@
     } else if (_cell == null) {
       _current = null;
       return false;
     } else {
       _current = _cell._element;
       _cell = _cell._next;
       return true;
     }
   }
 }