Fix System.IO.Pipelines reference assembly (#27644)

* Fix pipelines referency assembly

* Only include System.Threading.Tasks when needed (on netstandard11).

* Revert changes to ref csproj

Author: ahsonkhan

src/System.IO.Pipelines/ref/System.IO.Pipelines.cs

@@ -80,8 +80,8 @@ protected PipeWriter() { }
         public abstract void CancelPendingFlush();
         public abstract void Complete(System.Exception exception = null);
         public abstract System.IO.Pipelines.PipeAwaiter<System.IO.Pipelines.FlushResult> FlushAsync(System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken));
-        public abstract System.Memory<byte> GetMemory(int minimumLength = 0);
-        public abstract System.Span<byte> GetSpan(int minimumLength = 0);
+        public abstract System.Memory<byte> GetMemory(int sizeHint = 0);
+        public abstract System.Span<byte> GetSpan(int sizeHint = 0);
         public abstract void OnReaderCompleted(System.Action<System.Exception, object> callback, object state);
         public virtual System.IO.Pipelines.PipeAwaiter<System.IO.Pipelines.FlushResult> WriteAsync(System.ReadOnlyMemory<byte> source, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
     }

src/System.IO.Pipelines/ref/System.IO.Pipelines.csproj

@@ -16,8 +16,8 @@
     <Reference Include="System.Threading.Tasks" />
   </ItemGroup>
   <ItemGroup>
-    <ProjectReference Include="..\..\System.Memory\ref\System.Memory.csproj" />
     <ProjectReference Include="..\..\System.Buffers\ref\System.Buffers.csproj" />
+    <ProjectReference Include="..\..\System.Memory\ref\System.Memory.csproj" />
   </ItemGroup>
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />
 </Project>

src/System.IO.Pipelines/src/System.IO.Pipelines.csproj

@@ -53,7 +53,7 @@
     <Reference Include="System.Runtime" />
     <Reference Include="System.Runtime.Extensions" />
     <Reference Include="System.Threading" />
-    <Reference Include="System.Threading.Tasks" />
+    <Reference Include="System.Threading.Tasks" Condition="'$(TargetGroup)' == 'netstandard1.1'" />
     <Reference Include="System.Threading.ThreadPool" Condition="'$(TargetGroup)' != 'netstandard1.1'" />
   </ItemGroup>
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.targets))\dir.targets" />