[dotnet] Be more defensive when shutting down BiDi WebSocket

Author: jimevans

dotnet/src/webdriver/DevTools/DevToolsSession.cs

@@ -55,8 +55,6 @@ public class DevToolsSession : IDevToolsSession
 
         private DevToolsDomains domains;
 
-        private readonly SemaphoreSlim semaphoreSlimForSocketSend = new SemaphoreSlim(1, 1);
-
         /// <summary>
         /// Initializes a new instance of the DevToolsSession class, using the specified WebSocket endpoint.
         /// </summary>
@@ -219,18 +217,7 @@ public T GetVersionSpecificDomains<T>() where T : DevToolsSessionDomains
 
                 string contents = JsonConvert.SerializeObject(message);
                 this.pendingCommands.TryAdd(message.CommandId, message);
-
-                // socket SendAsync cannot be ran simultaneously, waiting available single worker
-                await semaphoreSlimForSocketSend.WaitAsync(cancellationToken);
-
-                try
-                {
-                    await this.connection.SendData(contents);
-                }
-                finally
-                {
-                    semaphoreSlimForSocketSend.Release();
-                }
+                await this.connection.SendData(contents);
 
                 var responseWasReceived = await Task.Run(() => message.SyncEvent.Wait(millisecondsTimeout.Value, cancellationToken));
 
@@ -335,7 +322,7 @@ protected void Dispose(bool disposing)
                 {
                     this.Domains.Target.TargetDetached -= this.OnTargetDetached;
                     this.pendingCommands.Clear();
-                    this.TerminateSocketConnection().GetAwaiter().GetResult();
+                    Task.Run(async () => await this.TerminateSocketConnection()).GetAwaiter().GetResult();
                 }
 
                 this.isDisposed = true;

dotnet/src/webdriver/DevTools/WebSocketConnection.cs

@@ -186,6 +186,10 @@ protected virtual async Task CloseClientWebSocket()
             {
                 // An OperationCanceledException is normal upon task/token cancellation, so disregard it
             }
+            catch (WebSocketException e)
+            {
+                this.Log($"Unexpected error during attempt at close: {e.Message}", DevToolsSessionLogLevel.Error);
+            }
         }
 
         /// <summary>

dotnet/test/common/DevTools/DevToolsTestFixture.cs

@@ -39,6 +39,7 @@ public void Teardown()
             {
                 session.Dispose();
                 EnvironmentManager.Instance.CloseCurrentDriver();
+                session = null;
                 driver = null;
             }
         }