Exposing event for after driver service process has started in .NET

This commit adds an event that fires after a driver service process
has started and is ready to receive commands from the local end.
The DriverServiceStartedEventArgs provides properties for the process
ID, a StreamReader for stdout, and a StreamReader for stderr. Combined
with the DriverServiceStarting event, the .NET bindings now allow the
user to completely silently start a driver service executable, and
to capture all of the diagnostic output written to the console by that
driver service.

dotnet/src/webdriver/DriverProcessStartedEventArgs.cs

@@ -0,0 +1,72 @@
+// <copyright file="DriverProcessStartedEventArgs.cs" company="WebDriver Committers">
+// Licensed to the Software Freedom Conservancy (SFC) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The SFC licenses this file
+// to you under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+using System;
+using System.Diagnostics;
+using System.IO;
+
+namespace OpenQA.Selenium
+{
+    /// <summary>
+    /// Provides data for the DriverProcessStarted event of a <see cref="DriverService"/> object.
+    /// </summary>
+    public class DriverProcessStartedEventArgs : EventArgs
+    {
+        private int processId;
+        private StreamReader standardOutputStreamReader;
+        private StreamReader standardErrorStreamReader;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DriverProcessStartingEventArgs"/> class.
+        /// </summary>
+        /// <param name="startInfo">The <see cref="ProcessStartInfo"/> of the
+        /// driver process to be started.</param>
+        public DriverProcessStartedEventArgs(Process driverProcess)
+        {
+            this.processId = driverProcess.Id;
+            this.standardOutputStreamReader = driverProcess.StandardOutput;
+            this.standardErrorStreamReader = driverProcess.StandardError;
+        }
+
+        /// <summary>
+        /// Gets the unique ID of the driver executable process.
+        /// </summary>
+        public int ProcessId
+        {
+            get { return this.processId; }
+        }
+
+        /// <summary>
+        /// Gets a <see cref="StreamReader"/> object that can be used to read the contents
+        /// printed to stdout by a driver service process.
+        /// </summary>
+        public StreamReader StandardOutputStreamReader
+        {
+            get { return this.standardOutputStreamReader; }
+        }
+
+        /// <summary>
+        /// Gets a <see cref="StreamReader"/> object that can be used to read the contents
+        /// printed to stderr by a driver service process.
+        /// </summary>
+        public StreamReader StandardErrorStreamReader
+        {
+            get { return standardErrorStreamReader; }
+        }
+    }
+}

dotnet/src/webdriver/DriverService.cs

@@ -73,10 +73,15 @@ protected DriverService(string servicePath, int port, string driverServiceExecut
         }
 
         /// <summary>
-        /// Occurs when the driver process starts is starting. 
+        /// Occurs when the driver process is starting. 
         /// </summary>
         public event EventHandler<DriverProcessStartingEventArgs> DriverProcessStarting;
 
+        /// <summary>
+        /// Occurs when the driver process has completely started. 
+        /// </summary>
+        public event EventHandler<DriverProcessStartedEventArgs> DriverProcessStarted;
+
         /// <summary>
         /// Gets the Uri of the service.
         /// </summary>
@@ -261,6 +266,8 @@ public void Start()
 
             this.driverServiceProcess.Start();
             bool serviceAvailable = this.WaitForServiceInitialization();
+            DriverProcessStartedEventArgs processStartedEventArgs = new DriverProcessStartedEventArgs(this.driverServiceProcess);
+            this.OnDriverProcessStarted(processStartedEventArgs);
 
             if (!serviceAvailable)
             {
@@ -323,6 +330,23 @@ protected void OnDriverProcessStarting(DriverProcessStartingEventArgs eventArgs)
             }
         }
 
+        /// <summary>
+        /// Raises the <see cref="DriverProcessStarted"/> event.
+        /// </summary>
+        /// <param name="eventArgs">A <see cref="DriverProcessStartedEventArgs"/> that contains the event data.</param>
+        protected void OnDriverProcessStarted(DriverProcessStartedEventArgs eventArgs)
+        {
+            if (eventArgs == null)
+            {
+                throw new ArgumentNullException("eventArgs", "eventArgs must not be null");
+            }
+
+            if (this.DriverProcessStarted != null)
+            {
+                this.DriverProcessStarted(this, eventArgs);
+            }
+        }
+
         /// <summary>
         /// Stops the DriverService.
         /// </summary>