Fix analyzer warnings related to SemanticsListener

These were introduced by the recent engine roll.

packages/flutter/lib/src/rendering/binding.dart

@@ -65,8 +65,8 @@ abstract class Renderer extends Scheduler
     renderView.configuration = new ViewConfiguration(size: ui.window.size);
   }
 
-  mojom.SemanticsClient _semanticsClient;
-  void setSemanticsClient(mojom.SemanticsClient client) {
+  mojom.SemanticsListener _semanticsClient;
+  void setSemanticsClient(mojom.SemanticsListener client) {
     assert(_semanticsClient == null);
     _semanticsClient = client;
     if (renderView != null)

packages/flutter/lib/src/rendering/semantics.dart

@@ -333,7 +333,7 @@ class SemanticsNode extends AbstractNode {
     return result;
   }
 
-  static void sendSemanticsTreeTo(mojom.SemanticsClient client) {
+  static void sendSemanticsTreeTo(mojom.SemanticsListener client) {
     for (SemanticsNode oldNode in _detachedNodes) {
       // The other side will have forgotten this node if we even send
       // it again, so make sure to mark it dirty so that it'll get
@@ -427,6 +427,8 @@ class SemanticsNode extends AbstractNode {
 }
 
 class SemanticsServer extends mojom.SemanticsServer {
+  void addSemanticsListener(mojom.SemanticsListener listener) {
+  }
   void tap(int nodeID) {
     SemanticsNode.getSemanticActionHandlerForId(nodeID, neededFlag: _SemanticFlags.canBeTapped)?.handleSemanticTap();
   }

packages/flutter/lib/src/widgets/semantics_debugger.dart

@@ -7,7 +7,7 @@ import 'dart:ui' as ui;
 
 import 'package:flutter/painting.dart';
 import 'package:flutter/rendering.dart';
-import 'package:sky_services/semantics/semantics.mojom.dart' as engine;
+import 'package:sky_services/semantics/semantics.mojom.dart' as mojom;
 
 import 'basic.dart';
 import 'framework.dart';
@@ -22,11 +22,11 @@ class SemanticsDebugger extends StatefulComponent {
 class _SemanticsDebuggerState extends State<SemanticsDebugger> {
   void initState() {
     super.initState();
-    _SemanticsDebuggerClient.ensureInstantiated();
-    _SemanticsDebuggerClient.instance.addListener(_update);
+    _SemanticsDebuggerListener.ensureInstantiated();
+    _SemanticsDebuggerListener.instance.addListener(_update);
   }
   void dispose() {
-    _SemanticsDebuggerClient.instance.removeListener(_update);
+    _SemanticsDebuggerListener.instance.removeListener(_update);
     super.dispose();
   }
   void _update() {
@@ -42,28 +42,28 @@ class _SemanticsDebuggerState extends State<SemanticsDebugger> {
   }
   void _handleTap() {
     assert(_lastPointerDownLocation != null);
-    _SemanticsDebuggerClient.instance.handleTap(_lastPointerDownLocation);
+    _SemanticsDebuggerListener.instance.handleTap(_lastPointerDownLocation);
     setState(() {
       _lastPointerDownLocation = null;
     });
   }
   void _handleLongPress() {
     assert(_lastPointerDownLocation != null);
-    _SemanticsDebuggerClient.instance.handleLongPress(_lastPointerDownLocation);
+    _SemanticsDebuggerListener.instance.handleLongPress(_lastPointerDownLocation);
     setState(() {
       _lastPointerDownLocation = null;
     });
   }
   void _handlePanEnd(Offset velocity) {
     assert(_lastPointerDownLocation != null);
-    _SemanticsDebuggerClient.instance.handlePanEnd(_lastPointerDownLocation, velocity);
+    _SemanticsDebuggerListener.instance.handlePanEnd(_lastPointerDownLocation, velocity);
     setState(() {
       _lastPointerDownLocation = null;
     });
   }
   Widget build(BuildContext context) {
     return new CustomPaint(
-      foregroundPainter: new _SemanticsDebuggerPainter(_SemanticsDebuggerClient.instance.generation, _lastPointerDownLocation),
+      foregroundPainter: new _SemanticsDebuggerPainter(_SemanticsDebuggerListener.instance.generation, _lastPointerDownLocation),
       child: new GestureDetector(
         behavior: HitTestBehavior.opaque,
         onTap: _handleTap,
@@ -233,16 +233,16 @@ class _SemanticsDebuggerEntry {
   }
 }
 
-class _SemanticsDebuggerClient implements engine.SemanticsClient {
-  _SemanticsDebuggerClient._() {
+class _SemanticsDebuggerListener implements mojom.SemanticsListener {
+  _SemanticsDebuggerListener._() {
     Renderer.instance.setSemanticsClient(this);
   }
 
-  static _SemanticsDebuggerClient instance;
-  static engine.SemanticsServer _server;
-  static void ensureInstantiated({ engine.SemanticsServer server }) {
+  static _SemanticsDebuggerListener instance;
+  static mojom.SemanticsServer _server;
+  static void ensureInstantiated({ mojom.SemanticsServer server }) {
     _server = server ?? new SemanticsServer();
-    instance ??= new _SemanticsDebuggerClient._();
+    instance ??= new _SemanticsDebuggerListener._();
   }
 
   Set<VoidCallback> _listeners = new Set<VoidCallback>();
@@ -256,7 +256,7 @@ class _SemanticsDebuggerClient implements engine.SemanticsClient {
 
   Map<int, _SemanticsDebuggerEntry> nodes = <int, _SemanticsDebuggerEntry>{};
 
-  _SemanticsDebuggerEntry _updateNode(engine.SemanticsNode node) {
+  _SemanticsDebuggerEntry _updateNode(mojom.SemanticsNode node) {
     _SemanticsDebuggerEntry entry = nodes.putIfAbsent(node.id, () => new _SemanticsDebuggerEntry(node.id));
     if (node.flags != null) {
       entry.canBeTapped = node.flags.canBeTapped;
@@ -295,7 +295,7 @@ class _SemanticsDebuggerClient implements engine.SemanticsClient {
       Set oldChildren = new Set<_SemanticsDebuggerEntry>.from(entry.children ?? const <_SemanticsDebuggerEntry>[]);
       entry.children?.clear();
       entry.children ??= new List<_SemanticsDebuggerEntry>();
-      for (engine.SemanticsNode child in node.children)
+      for (mojom.SemanticsNode child in node.children)
         entry.children.add(_updateNode(child));
       Set newChildren = new Set<_SemanticsDebuggerEntry>.from(entry.children);
       Set<_SemanticsDebuggerEntry> removedChildren = oldChildren.difference(newChildren);
@@ -307,9 +307,9 @@ class _SemanticsDebuggerClient implements engine.SemanticsClient {
 
   int generation = 0;
 
-  updateSemanticsTree(List<engine.SemanticsNode> nodes) {
+  updateSemanticsTree(List<mojom.SemanticsNode> nodes) {
     generation += 1;
-    for (engine.SemanticsNode node in nodes)
+    for (mojom.SemanticsNode node in nodes)
       _updateNode(node);
     for (VoidCallback listener in _listeners)
       listener();
@@ -347,9 +347,9 @@ class _SemanticsDebuggerPainter extends CustomPainter {
   final int generation;
   final Point pointerPosition;
   void paint(Canvas canvas, Size size) {
-    _SemanticsDebuggerClient.instance.nodes[0]?.paint(
+    _SemanticsDebuggerListener.instance.nodes[0]?.paint(
       canvas,
-      _SemanticsDebuggerClient.instance.nodes[0].findDepth()
+      _SemanticsDebuggerListener.instance.nodes[0].findDepth()
     );
     if (pointerPosition != null) {
       Paint paint = new Paint();

packages/flutter/test/widget/buttons_test.dart

@@ -12,7 +12,7 @@ import 'test_semantics.dart';
 void main() {
   test('Does FlatButton contribute semantics', () {
     testWidgets((WidgetTester tester) {
-      TestSemanticsClient client = new TestSemanticsClient();
+      TestSemanticsListener client = new TestSemanticsListener();
       tester.pumpWidget(
         new Material(
           child: new Center(

packages/flutter/test/widget/semantics_1_test.dart

@@ -13,7 +13,7 @@ import 'test_semantics.dart';
 void main() {
   test('Semantics 1', () {
     testWidgets((WidgetTester tester) {
-      TestSemanticsClient client = new TestSemanticsClient();
+      TestSemanticsListener client = new TestSemanticsListener();
 
       // smoketest
       tester.pumpWidget(

packages/flutter/test/widget/semantics_2_test.dart

@@ -13,7 +13,7 @@ import 'test_semantics.dart';
 void main() {
   test('Semantics 2', () {
     testWidgets((WidgetTester tester) {
-      TestSemanticsClient client = new TestSemanticsClient();
+      TestSemanticsListener client = new TestSemanticsListener();
 
       // this test is the same as the test in Semantics 1, but
       // starting with the second branch being ignored and then

packages/flutter/test/widget/semantics_3_test.dart

@@ -12,7 +12,7 @@ import 'test_semantics.dart';
 void main() {
   test('Semantics 3', () {
     testWidgets((WidgetTester tester) {
-      TestSemanticsClient client = new TestSemanticsClient();
+      TestSemanticsListener client = new TestSemanticsListener();
 
       // implicit annotators
       tester.pumpWidget(

packages/flutter/test/widget/semantics_4_test.dart

@@ -12,7 +12,7 @@ import 'test_semantics.dart';
 void main() {
   test('Semantics 4', () {
     testWidgets((WidgetTester tester) {
-      TestSemanticsClient client = new TestSemanticsClient();
+      TestSemanticsListener client = new TestSemanticsListener();
 
       //    O
       //   / \       O=root

packages/flutter/test/widget/semantics_5_test.dart

@@ -12,7 +12,7 @@ import 'test_semantics.dart';
 void main() {
   test('Semantics 5', () {
     testWidgets((WidgetTester tester) {
-      TestSemanticsClient client = new TestSemanticsClient();
+      TestSemanticsListener client = new TestSemanticsListener();
 
       tester.pumpWidget(
         new Stack(

packages/flutter/test/widget/test_semantics.dart

@@ -3,15 +3,15 @@
 // found in the LICENSE file.
 
 import 'package:flutter/rendering.dart';
-import 'package:sky_services/semantics/semantics.mojom.dart' as engine;
+import 'package:sky_services/semantics/semantics.mojom.dart' as mojom;
 
-class TestSemanticsClient implements engine.SemanticsClient {
-  TestSemanticsClient() {
+class TestSemanticsListener implements mojom.SemanticsListener {
+  TestSemanticsListener() {
     Renderer.instance.setSemanticsClient(this);
   }
-  final List<engine.SemanticsNode> updates = <engine.SemanticsNode>[];
-  updateSemanticsTree(List<engine.SemanticsNode> nodes) {
-    assert(!nodes.any((engine.SemanticsNode node) => node == null));
+  final List<mojom.SemanticsNode> updates = <mojom.SemanticsNode>[];
+  updateSemanticsTree(List<mojom.SemanticsNode> nodes) {
+    assert(!nodes.any((mojom.SemanticsNode node) => node == null));
     updates.addAll(nodes);
     updates.add(null);
   }

packages/flutter/test/widget/tooltip_test.dart

@@ -359,7 +359,7 @@ void main() {
 
   test('Does tooltip contribute semantics', () {
     testWidgets((WidgetTester tester) {
-      TestSemanticsClient client = new TestSemanticsClient();
+      TestSemanticsListener client = new TestSemanticsListener();
       GlobalKey key = new GlobalKey();
       tester.pumpWidget(
         new Overlay(