Fixes to patch files necessary to use the analyzer

sdk/lib/_internal/js_runtime/lib/developer_patch.dart

Index: sdk/lib/_internal/js_runtime/lib/developer_patch.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/developer_patch.dart b/sdk/lib/_internal/js_runtime/lib/developer_patch.dart
index 541658b12897eabaea9dd4738af05f9d3195ed4e..4cefe98820cdd4dc8bd15be1b1d44265ec526b43 100644
--- a/sdk/lib/_internal/js_runtime/lib/developer_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/developer_patch.dart
@@ -46,7 +46,7 @@ _registerExtension(String method, ServiceExtensionHandler handler) {
 }
 
 @patch
-_postEvent(String eventKind, String eventData) {
+void _postEvent(String eventKind, String eventData) {

[Kevin Millikin (Google), 2017/01/04 15:31:04]

Patch files cannot change the return type.  In this case, the SDK's return type
is omitted (i.e., dynamic) and the VM's return type is void.

I've just changed the SDK's return type to be void too, because it's better.

   // TODO.
 }
 
@@ -129,4 +129,51 @@ void _webServerControl(SendPort sendPort, bool enable) {
 @patch
 String _getIsolateIDFromSendPort(SendPort sendPort) {
   return null;
-}
+}
+
+@patch
+class UserTag {
+  @patch
+  factory UserTag(String label) = _FakeUserTag;
+
+  @patch
+  static UserTag get defaultTag => _FakeUserTag._defaultTag;
+}
+
+class _FakeUserTag implements UserTag {

[Kevin Millikin (Google), 2017/01/04 15:31:04]

This implementation machinery was in the SDK and ignored by the VM (it patched
members that were not declared external, which isn't actually allowed).

I've moved it to the dart2js patch here and declared the members external.

+  static Map _instances = {};
+
+  _FakeUserTag.real(this.label);
+
+  factory _FakeUserTag(String label) {
+    // Canonicalize by name.
+    var existingTag = _instances[label];
+    if (existingTag != null) {
+      return existingTag;
+    }
+    // Throw an exception if we've reached the maximum number of user tags.
+    if (_instances.length == UserTag.MAX_USER_TAGS) {
+      throw new UnsupportedError(
+          'UserTag instance limit (${UserTag.MAX_USER_TAGS}) reached.');
+    }
+    // Create a new instance and add it to the instance map.
+    var instance = new _FakeUserTag.real(label);
+    _instances[label] = instance;
+    return instance;
+  }
+
+  final String label;
+
+  UserTag makeCurrent() {
+    var old = _currentTag;
+    _currentTag = this;
+    return old;
+  }
+
+  static final UserTag _defaultTag = new _FakeUserTag('Default');
+}
+
+var _currentTag = _FakeUserTag._defaultTag;
+
+@patch
+UserTag getCurrentTag() => _currentTag;