Mirror changes from dotnet/coreclr (#28534)

* Adding Memory.Pin() to eventually replace Memory.Retain(bool) (#17269)

* Adding Memory.Pin() to eventually replace Memory.Retain(bool)

* Fix copy/paste error and return default for when object is null.

* Fix XML comments.

Signed-off-by: dotnet-bot-corefx-mirror <dotnet-bot@microsoft.com>

* Add Memory.Pin to the ref and add tests.

* Add Pin tests

* Update calls to Retain(true) to now call Pin()

* Remove extra space in tests.

* Add Pin to the ApiCompatBaseline for uapaot.

1 files changed, 2 insertions, 7 deletions

diff --git a/src/System.Memory/tests/Memory/Strings.cs b/src/System.Memory/tests/Memory/Strings.cs
index 6e4e0bfe05..b711179cd1 100644
--- a/src/System.Memory/tests/Memory/Strings.cs
+++ b/src/System.Memory/tests/Memory/Strings.cs
@@ -57,18 +57,13 @@ namespace System.MemoryTests
         }
 
         [Fact]
-        public static unsafe void Memory_Retain_ExpectedPointerValue()
+        public static unsafe void Memory_Pin_ExpectedPointerValue()
         {
             string input = "0123456789";
             ReadOnlyMemory<char> readonlyMemory = input.AsMemory();
             Memory<char> m = MemoryMarshal.AsMemory(readonlyMemory);
 
-            using (MemoryHandle h = m.Retain(pin: false))
-            {
-                Assert.Equal(IntPtr.Zero, (IntPtr)h.Pointer);
-            }
-
-            using (MemoryHandle h = m.Retain(pin: true))
+            using (MemoryHandle h = m.Pin())
             {
                 GC.Collect();
                 fixed (char* ptr = input)