Use metadata for patching.

sdk/lib/_internal/lib/collection_patch.dart

Index: sdk/lib/_internal/lib/collection_patch.dart
diff --git a/sdk/lib/_internal/lib/collection_patch.dart b/sdk/lib/_internal/lib/collection_patch.dart
index 0c19fdbd35b35f6c5766e0439cb8b4e68ff31cf6..78147f8871f13771f89f8f311f881f7b9021a51e 100644
--- a/sdk/lib/_internal/lib/collection_patch.dart
+++ b/sdk/lib/_internal/lib/collection_patch.dart
@@ -4,12 +4,14 @@
 
 // Patch file for dart:collection classes.
 import 'dart:_foreign_helper' show JS;
-import 'dart:_js_helper' show fillLiteralMap, NoInline;
-
-patch class HashMap<K, V> {
-  patch factory HashMap({ bool equals(K key1, K key2),
-                          int hashCode(K key),
-                          bool isValidKey(potentialKey) }) {
+import 'dart:_js_helper' show fillLiteralMap, NoInline, 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) {
@@ -36,7 +38,8 @@ patch class HashMap<K, V> {
     return new _CustomHashMap<K, V>(equals, hashCode, isValidKey);
   }
 
-  patch factory HashMap.identity() = _IdentityHashMap<K, V>;
+  @patch
+  factory HashMap.identity() = _IdentityHashMap<K, V>;
 }
 
 class _HashMap<K, V> implements HashMap<K, V> {
@@ -478,10 +481,12 @@ class HashMapKeyIterator<E> implements Iterator<E> {
   }
 }
 
-patch class LinkedHashMap<K, V> {
-  patch factory LinkedHashMap({ bool equals(K key1, K key2),
-                                int hashCode(K key),
-                                bool isValidKey(potentialKey) }) {
+@patch
+class LinkedHashMap<K, V> {
+  @patch
+  factory LinkedHashMap({ bool equals(K key1, K key2),
+                          int hashCode(K key),
+                          bool isValidKey(potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
@@ -508,7 +513,8 @@ patch class LinkedHashMap<K, V> {
     return new _LinkedCustomHashMap<K, V>(equals, hashCode, isValidKey);
   }
 
-  patch factory LinkedHashMap.identity() = _LinkedIdentityHashMap<K, V>;
+  @patch
+  factory LinkedHashMap.identity() = _LinkedIdentityHashMap<K, V>;
 
   // Private factory constructor called by generated code for map literals.
   @NoInline()
@@ -959,10 +965,12 @@ class LinkedHashMapKeyIterator<E> implements Iterator<E> {
   }
 }
 
-patch class HashSet<E> {
-  patch factory HashSet({ bool equals(E e1, E e2),
-                          int hashCode(E e),
-                          bool isValidKey(potentialKey) }) {
+@patch
+class HashSet<E> {
+  @patch
+  factory HashSet({ bool equals(E e1, E e2),
+                    int hashCode(E e),
+                    bool isValidKey(potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
@@ -989,7 +997,8 @@ patch class HashSet<E> {
     return new _CustomHashSet<E>(equals, hashCode, isValidKey);
   }
 
-  patch factory HashSet.identity() = _IdentityHashSet<E>;
+  @patch
+  factory HashSet.identity() = _IdentityHashSet<E>;
 }
 
 class _HashSet<E> extends _HashSetBase<E> implements HashSet<E> {
@@ -1361,10 +1370,12 @@ class HashSetIterator<E> implements Iterator<E> {
   }
 }
 
-patch class LinkedHashSet<E> {
-  patch factory LinkedHashSet({ bool equals(E e1, E e2),
-                                int hashCode(E e),
-                                bool isValidKey(potentialKey) }) {
+@patch
+class LinkedHashSet<E> {
+  @patch
+  factory LinkedHashSet({ bool equals(E e1, E e2),
+                          int hashCode(E e),
+                          bool isValidKey(potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
@@ -1391,7 +1402,8 @@ patch class LinkedHashSet<E> {
     return new _LinkedCustomHashSet<E>(equals, hashCode, isValidKey);
   }
 
-  patch factory LinkedHashSet.identity() = _LinkedIdentityHashSet<E>;
+  @patch
+  factory LinkedHashSet.identity() = _LinkedIdentityHashSet<E>;
 }
 
 class _LinkedHashSet<E> extends _HashSetBase<E> implements LinkedHashSet<E> {