Elements. Changes to support google3 migration.

Change-Id: I3244d230632dd237304148f7f62f9719d3ac7c11
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/401982
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer/lib/dart/element/type.dart

@@ -385,6 +385,11 @@ abstract class InterfaceType implements ParameterizedType {
   /// with the given name.
   MethodElement? getMethod(String name);
 
+  /// Return the element representing the method with the given [name] that is
+  /// declared in this class, or `null` if this class does not declare a method
+  /// with the given name.
+  MethodElement2? getMethod2(String name);
+
   /// Return the element representing the setter with the given [name] that is
   /// declared in this class, or `null` if this class does not declare a setter
   /// with the given name.

pkg/analyzer/lib/src/dart/element/type.dart

@@ -905,6 +905,11 @@ class InterfaceTypeImpl extends TypeImpl implements InterfaceType {
   MethodElement? getMethod(String methodName) =>
       MethodMember.from(element.getMethod(methodName), this);
 
+  @override
+  MethodElement2? getMethod2(String methodName) {
+    return getMethod(methodName)?.asElement2;
+  }
+
   @override
   PropertyAccessorElement? getSetter(String setterName) =>
       PropertyAccessorMember.from(element.getSetter(setterName), this);

pkg/analyzer/lib/src/utilities/extensions/element.dart

@@ -375,12 +375,6 @@ extension InterfaceElementExtension on InterfaceElement {
   }
 }
 
-extension InterfaceTypeExtension on InterfaceType {
-  MethodElement2? getMethod2(String name) {
-    return getMethod(name)?.asElement2;
-  }
-}
-
 extension LabelElement2Extension on LabelElement2 {
   LabelElement get asElement {
     return firstFragment as LabelElement;