Avoid accessing a disposed CancellationSeries

[sharwell]

Fixes an error observed in integration test logs:

06/08/2021 01:28:51 Coordinated Universal Time: Error : 1 :[devenv:7680] Unexpected exception: System.AggregateException: One or more errors occurred. ---> System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'CancellationSeries'.
   at Roslyn.Utilities.CancellationSeries.CreateNext(CancellationToken token) in /_/src/Workspaces/Core/Portable/Utilities/CancellationSeries.cs:line 105
   at Microsoft.CodeAnalysis.Editor.Implementation.Classification.CompilationAvailableTaggerEventSource.OnEventSourceChanged(Object sender, TaggerEventArgs args) in /_/src/EditorFeatures/Core/Implementation/Classification/CompilationAvailableTaggerEventSource.cs:line 77
   at Microsoft.CodeAnalysis.Editor.Shared.Tagging.AbstractTaggerEventSource.RaiseChanged() in /_/src/EditorFeatures/Core/Shared/Tagging/EventSources/AbstractTaggerEventSource.cs:line 22
   at Microsoft.CodeAnalysis.Editor.Shared.Tagging.TaggerEventSources.WorkspaceChangedEventSource.<.ctor>b__1_0(CancellationToken cancellationToken) in /_/src/EditorFeatures/Core/Shared/Tagging/EventSources/TaggerEventSources.WorkspaceChangedEventSource.cs:line 31
   at Roslyn.Utilities.AsyncBatchingDelay.OnNotifyAsync(ImmutableArray`1 _, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingDelay.cs:line 41
   at Roslyn.Utilities.AsyncBatchingWorkQueue`1.ProcessNextBatchAsync(CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue.cs:line 190
   at Roslyn.Utilities.AsyncBatchingWorkQueue`1.<TryKickOffNextBatchTask>b__16_1(Task _) in /_/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue.cs:line 166
   at Roslyn.Utilities.TaskExtensions.<>c__DisplayClass26_1.<ContinueWithAfterDelayFromAsync>b__1(Task`1 _) in /_/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/TaskExtensions.cs:line 502
   at System.Threading.Tasks.ContinuationResultTaskFromResultTask`2.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
   --- End of inner exception stack trace ---
   at Microsoft.CodeAnalysis.ErrorReporting.WatsonExtensions.SetCallstackIfEmpty(Exception exception) in /_/src/VisualStudio/Core/Def/Implementation/Watson/WatsonExtensions.cs:line 110
---> (Inner Exception #0) System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'CancellationSeries'.
   at Roslyn.Utilities.CancellationSeries.CreateNext(CancellationToken token) in /_/src/Workspaces/Core/Portable/Utilities/CancellationSeries.cs:line 105
   at Microsoft.CodeAnalysis.Editor.Implementation.Classification.CompilationAvailableTaggerEventSource.OnEventSourceChanged(Object sender, TaggerEventArgs args) in /_/src/EditorFeatures/Core/Implementation/Classification/CompilationAvailableTaggerEventSource.cs:line 77
   at Microsoft.CodeAnalysis.Editor.Shared.Tagging.AbstractTaggerEventSource.RaiseChanged() in /_/src/EditorFeatures/Core/Shared/Tagging/EventSources/AbstractTaggerEventSource.cs:line 22
   at Microsoft.CodeAnalysis.Editor.Shared.Tagging.TaggerEventSources.WorkspaceChangedEventSource.<.ctor>b__1_0(CancellationToken cancellationToken) in /_/src/EditorFeatures/Core/Shared/Tagging/EventSources/TaggerEventSources.WorkspaceChangedEventSource.cs:line 31
   at Roslyn.Utilities.AsyncBatchingDelay.OnNotifyAsync(ImmutableArray`1 _, CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingDelay.cs:line 41
   at Roslyn.Utilities.AsyncBatchingWorkQueue`1.ProcessNextBatchAsync(CancellationToken cancellationToken) in /_/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue.cs:line 190
   at Roslyn.Utilities.AsyncBatchingWorkQueue`1.<TryKickOffNextBatchTask>b__16_1(Task _) in /_/src/Workspaces/Core/Portable/Shared/Utilities/AsyncBatchingWorkQueue.cs:line 166
   at Roslyn.Utilities.TaskExtensions.<>c__DisplayClass26_1.<ContinueWithAfterDelayFromAsync>b__1(Task`1 _) in /_/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Utilities/TaskExtensions.cs:line 502
   at System.Threading.Tasks.ContinuationResultTaskFromResultTask`2.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()<---

[CyrusNajmabadi]

it very much feels like it takse a bunch of extra tuff just to properly handle cancellation lifetime :(

[sharwell]

When the object is both disposable and asynchronous, yes.

The problem was always known. The difference here is the problem and fix are visible.