Avoid Task allocation on GetInfoForMetadataReferenceAsync fast path

src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/ExtensionMethodImportCompletionHelper.ExtensionMethodSymbolComputer.cs

@@ -84,7 +84,7 @@ public Task PopulateIndicesAsync(CancellationToken cancellationToken)
                 foreach (var peReference in GetAllRelevantPeReferences())
                 {
                     tasks.Add(Task.Run(()
-                        => SymbolTreeInfo.GetInfoForMetadataReferenceAsync(Solution, peReference, loadOnly: false, cancellationToken), cancellationToken));
+                        => SymbolTreeInfo.GetInfoForMetadataReferenceAsync(Solution, peReference, loadOnly: false, cancellationToken).AsTask(), cancellationToken));
                 }
 
                 return Task.WhenAll(tasks.ToImmutable());
@@ -100,7 +100,7 @@ public async Task<(ImmutableArray<IMethodSymbol> symbols, bool isPartialResult)>
                     tasks.Add(Task.Run(() => GetExtensionMethodSymbolsFromPeReferenceAsync(
                         peReference,
                         forceIndexCreation,
-                        cancellationToken), cancellationToken));
+                        cancellationToken).AsTask(), cancellationToken));
                 }
 
                 foreach (var project in GetAllRelevantProjects())
@@ -184,7 +184,7 @@ private ImmutableArray<PortableExecutableReference> GetAllRelevantPeReferences()
                     : GetExtensionMethodsForSymbolsFromDifferentCompilation(matchingMethodSymbols, cancellationToken);
             }
 
-            private async Task<ImmutableArray<IMethodSymbol>?> GetExtensionMethodSymbolsFromPeReferenceAsync(
+            private async ValueTask<ImmutableArray<IMethodSymbol>?> GetExtensionMethodSymbolsFromPeReferenceAsync(
                 PortableExecutableReference peReference,
                 bool forceIndexCreation,
                 CancellationToken cancellationToken)

src/Features/Core/Portable/IncrementalCaches/SymbolTreeInfoCacheService.cs

@@ -29,7 +29,7 @@ private class SymbolTreeInfoCacheService : ISymbolTreeInfoCacheService
                 _metadataIdToInfo = metadataIdToInfo;
             }
 
-            public async Task<SymbolTreeInfo> TryGetMetadataSymbolTreeInfoAsync(
+            public async ValueTask<SymbolTreeInfo> TryGetMetadataSymbolTreeInfoAsync(
                 Solution solution,
                 PortableExecutableReference reference,
                 CancellationToken cancellationToken)

src/Workspaces/Core/Portable/FindSymbols/SymbolTree/ISymbolTreeInfoCacheService.cs

@@ -20,6 +20,6 @@ internal interface ISymbolTreeInfoCacheService : IWorkspaceService
         /// <summary>
         /// Returns null if the info cannot be retrieved from the cache.
         /// </summary>
-        Task<SymbolTreeInfo> TryGetMetadataSymbolTreeInfoAsync(Solution solution, PortableExecutableReference reference, CancellationToken cancellationToken);
+        ValueTask<SymbolTreeInfo> TryGetMetadataSymbolTreeInfoAsync(Solution solution, PortableExecutableReference reference, CancellationToken cancellationToken);
     }
 }

src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo_Metadata.cs

@@ -65,7 +65,7 @@ private static Metadata GetMetadataNoThrow(PortableExecutableReference reference
             }
         }
 
-        public static Task<SymbolTreeInfo> GetInfoForMetadataReferenceAsync(
+        public static ValueTask<SymbolTreeInfo> GetInfoForMetadataReferenceAsync(
             Solution solution, PortableExecutableReference reference,
             bool loadOnly, CancellationToken cancellationToken)
         {
@@ -79,7 +79,8 @@ private static Metadata GetMetadataNoThrow(PortableExecutableReference reference
         /// Produces a <see cref="SymbolTreeInfo"/> for a given <see cref="PortableExecutableReference"/>.
         /// Note:  will never return null;
         /// </summary>
-        public static async Task<SymbolTreeInfo> GetInfoForMetadataReferenceAsync(
+        [PerformanceSensitive("https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1224834", OftenCompletesSynchronously = true)]
+        public static async ValueTask<SymbolTreeInfo> GetInfoForMetadataReferenceAsync(
             Solution solution,
             PortableExecutableReference reference,
             Checksum checksum,