[Mono.Android] JavaList.Add should allow duplicates.

Author: jpobst

src/Mono.Android/Android.Runtime/JavaList.cs

@@ -551,8 +551,6 @@ public virtual bool Add (Java.Lang.Object? item)
 
 		public virtual bool Add (int index, Java.Lang.Object? item)
 		{
-			if (Contains (item))
-				return false;
 			Add ((object?) item);
 			return true;
 		}

tests/Mono.Android-Tests/Java.Interop/JavaListTest.cs

@@ -15,6 +15,18 @@ namespace Java.InteropTests
 		[SetUp]
 		public void Setup () => list = new T ();
 
+		[Test]
+		public void Add ()
+		{
+			list.Add ("foo");
+			Assert.AreEqual ("foo", list [0]);
+
+			// Ensure duplicates are allowed.
+			list.Add ("foo");
+			Assert.AreEqual (2, list.Count);
+			Assert.AreEqual ("foo", list [1]);
+		}
+
 		[Test]
 		public void Count ()
 		{