Create AST structure for asserts in constructor initializers

pkg/analyzer/lib/dart/ast/visitor.dart

Index: pkg/analyzer/lib/dart/ast/visitor.dart
diff --git a/pkg/analyzer/lib/dart/ast/visitor.dart b/pkg/analyzer/lib/dart/ast/visitor.dart
index d3e55d33a9135374b754637355b823dd7b102ec6..599678e8977e048e1e6535c06eb515ffa3d9cf3a 100644
--- a/pkg/analyzer/lib/dart/ast/visitor.dart
+++ b/pkg/analyzer/lib/dart/ast/visitor.dart
@@ -165,6 +165,9 @@ class GeneralizingAstVisitor<R> implements AstVisitor<R> {
   R visitAsExpression(AsExpression node) => visitExpression(node);
 
   @override
+  R visitAssertInitializer(AssertInitializer node) => visitNode(node);
+
+  @override
   R visitAssertStatement(AssertStatement node) => visitStatement(node);
 
   @override
@@ -597,6 +600,12 @@ class RecursiveAstVisitor<R> implements AstVisitor<R> {
   }
 
   @override
+  R visitAssertInitializer(AssertInitializer node) {
+    node.visitChildren(this);
+    return null;
+  }
+
+  @override
   R visitAssertStatement(AssertStatement node) {
     node.visitChildren(this);
     return null;
@@ -1244,6 +1253,9 @@ class SimpleAstVisitor<R> implements AstVisitor<R> {
   R visitAsExpression(AsExpression node) => null;
 
   @override
+  R visitAssertInitializer(AssertInitializer node) => null;
+
+  @override
   R visitAssertStatement(AssertStatement node) => null;
 
   @override
@@ -1616,6 +1628,14 @@ class TimedAstVisitor<T> implements AstVisitor<T> {
   }
 
   @override
+  T visitAssertInitializer(AssertInitializer node) {
+    stopwatch.start();
+    T result = _baseVisitor.visitAssertInitializer(node);
+    stopwatch.stop();
+    return result;
+  }
+
+  @override
   T visitAssertStatement(AssertStatement node) {
     stopwatch.start();
     T result = _baseVisitor.visitAssertStatement(node);
@@ -2475,6 +2495,9 @@ class UnifyingAstVisitor<R> implements AstVisitor<R> {
   R visitAsExpression(AsExpression node) => visitNode(node);
 
   @override
+  R visitAssertInitializer(AssertInitializer node) => visitNode(node);
+
+  @override
   R visitAssertStatement(AssertStatement node) => visitNode(node);
 
   @override