Clarify scope of cancellation in Task.Run (#4253)

Author: breyed

xml/System.Threading.Tasks/Task.xml

@@ -3447,8 +3447,8 @@ Task t Status: RanToCompletion, Result: 42
       </Parameters>
       <Docs>
         <param name="action">The work to execute asynchronously</param>
-        <param name="cancellationToken">A cancellation token that can be used to cancel the work</param>
-        <summary>Queues the specified work to run on the thread pool and returns a <see cref="T:System.Threading.Tasks.Task" /> object that represents that work. A cancellation token allows the work to be cancelled.</summary>
+        <param name="cancellationToken">A cancellation token that can be used to cancel the work if it has not yet started. <see cref="M:System.Threading.Tasks.Task.Run(System.Action,System.Threading.CancellationToken)" /> does not pass <paramref name="cancellationToken" /> to <paramref name="action" />.</param>
+        <summary>Queues the specified work to run on the thread pool and returns a <see cref="T:System.Threading.Tasks.Task" /> object that represents that work. A cancellation token allows the work to be cancelled if it has not yet started.</summary>
         <returns>A task that represents the work queued to execute in the thread pool.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[  
@@ -3520,8 +3520,8 @@ Task t Status: RanToCompletion, Result: 42
       </Parameters>
       <Docs>
         <param name="function">The work to execute asynchronously.</param>
-        <param name="cancellationToken">A cancellation token that should be used to cancel the work.</param>
-        <summary>Queues the specified work to run on the thread pool and returns a proxy for the task returned by <paramref name="function" />.</summary>
+        <param name="cancellationToken">A cancellation token that can be used to cancel the work if it has not yet started. <see cref="M:System.Threading.Tasks.Task.Run(System.Func{System.Threading.Tasks.Task},System.Threading.CancellationToken)" /> does not pass <paramref name="cancellationToken" /> to <paramref name="action" />.</param>
+        <summary>Queues the specified work to run on the thread pool and returns a proxy for the task returned by <paramref name="function" />. A cancellation token allows the work to be cancelled if it has not yet started.</summary>
         <returns>A task that represents a proxy for the task returned by <paramref name="function" />.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[  
@@ -3581,7 +3581,7 @@ Task t Status: RanToCompletion, Result: 42
       <Docs>
         <typeparam name="TResult">The type of the result returned by the proxy task.</typeparam>
         <param name="function">The work to execute asynchronously</param>
-        <summary>Queues the specified work to run on the thread pool and returns a proxy for the <see langword="Task(TResult)" /> returned by <paramref name="function" />.</summary>
+        <summary>Queues the specified work to run on the thread pool and returns a proxy for the <see langword="Task(TResult)" /> returned by <paramref name="function" />. A cancellation token allows the work to be cancelled if it has not yet started.</summary>
         <returns>A <see langword="Task(TResult)" /> that represents a proxy for the <see langword="Task(TResult)" /> returned by <paramref name="function" />.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[  
@@ -3637,7 +3637,7 @@ Task t Status: RanToCompletion, Result: 42
       <Docs>
         <typeparam name="TResult">The return type of the task.</typeparam>
         <param name="function">The work to execute asynchronously.</param>
-        <summary>Queues the specified work to run on the thread pool and returns a <see cref="T:System.Threading.Tasks.Task`1" /> object that represents that work.</summary>
+        <summary>Queues the specified work to run on the thread pool and returns a <see cref="T:System.Threading.Tasks.Task`1" /> object that represents that work. A cancellation token allows the work to be cancelled if it has not yet started.</summary>
         <returns>A task object that represents the work queued to execute in the thread pool.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[  
@@ -3713,7 +3713,7 @@ Task t Status: RanToCompletion, Result: 42
       <Docs>
         <typeparam name="TResult">The type of the result returned by the proxy task.</typeparam>
         <param name="function">The work to execute asynchronously</param>
-        <param name="cancellationToken">A cancellation token that should be used to cancel the work</param>
+        <param name="cancellationToken">A cancellation token that can be used to cancel the work if it has not yet started. <see cref="M:System.Threading.Tasks.Task.Run``1(System.Func{System.Threading.Tasks.Task{``0}},System.Threading.CancellationToken)" /> does not pass <paramref name="cancellationToken" /> to <paramref name="action" />.</param>
         <summary>Queues the specified work to run on the thread pool and returns a proxy for the <see langword="Task(TResult)" /> returned by <paramref name="function" />.</summary>
         <returns>A <see langword="Task(TResult)" /> that represents a proxy for the <see langword="Task(TResult)" /> returned by <paramref name="function" />.</returns>
         <remarks>
@@ -3774,8 +3774,8 @@ Task t Status: RanToCompletion, Result: 42
       <Docs>
         <typeparam name="TResult">The result type of the task.</typeparam>
         <param name="function">The work to execute asynchronously</param>
-        <param name="cancellationToken">A cancellation token that should be used to cancel the work</param>
-        <summary>Queues the specified work to run on the thread pool and returns a <see langword="Task(TResult)" /> object that represents that work. A cancellation token allows the work to be cancelled.</summary>
+        <param name="cancellationToken">A cancellation token that can be used to cancel the work if it has not yet started. <see cref="M:System.Threading.Tasks.Task.Run``1(System.Func{``0},System.Threading.CancellationToken)" /> does not pass <paramref name="cancellationToken" /> to <paramref name="action" />.</param>
+        <summary>Queues the specified work to run on the thread pool and returns a <see langword="Task(TResult)" /> object that represents that work.</summary>
         <returns>A <see langword="Task(TResult)" /> that represents the work queued to execute in the thread pool.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[