Add work item attributes.

src/EditorFeatures/CSharpTest/AddParameter/AddParameterTests.cs

@@ -459,6 +459,7 @@ private void Foo()
 ignoreTrivia: false);
         }
 
+        [WorkItem(20973, "https://github.com/dotnet/roslyn/issues/20973")]
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddParameter)]
         public async Task TestNullArg1()
         {
@@ -491,6 +492,7 @@ void M()
 }");
         }
 
+        [WorkItem(20973, "https://github.com/dotnet/roslyn/issues/20973")]
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddParameter)]
         public async Task TestNullArg2()
         {
@@ -523,6 +525,7 @@ void M()
 }");
         }
 
+        [WorkItem(20973, "https://github.com/dotnet/roslyn/issues/20973")]
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddParameter)]
         public async Task TestDefaultArg1()
         {
@@ -555,6 +558,7 @@ void M()
 }");
         }
 
+        [WorkItem(20973, "https://github.com/dotnet/roslyn/issues/20973")]
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddParameter)]
         public async Task TestDefaultArg2()
         {

src/EditorFeatures/VisualBasicTest/AddParameter/AddParameterTests.vb

@@ -54,6 +54,7 @@ class D
 end class")
         End Function
 
+        <WorkItem(20973, "https://github.com/dotnet/roslyn/issues/20973")>
         <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddParameter)>
         Public Async Function TestNothingArgument1() As Task
             Await TestInRegularAndScriptAsync(