Support ChromeDriver "append log" flag in .NET

ChromeDriver has a command line option to append to existing log file
instead of overwriting it. Update .NET API to support it.

Signed-off-by: Jim Evans <james.h.evans.jr@gmail.com>

dotnet/src/webdriver/Chrome/ChromeDriverService.cs

@@ -37,6 +37,7 @@ public sealed class ChromeDriverService : DriverService
         private string whitelistedIpAddresses = string.Empty;
         private int adbPort = -1;
         private bool enableVerboseLogging;
+        private bool enableAppendLog;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ChromeDriverService"/> class.
@@ -95,6 +96,16 @@ public bool EnableVerboseLogging
             set { this.enableVerboseLogging = value; }
         }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether to enable appending to an existing ChromeDriver log file.
+        /// Defaults to <see langword="false"/>.
+        /// </summary>
+        public bool EnableAppendLog
+        {
+            get { return this.enableAppendLog; }
+            set { this.enableAppendLog = value; }
+        }
+
         /// <summary>
         /// Gets or sets the comma-delimited list of IP addresses that are approved to
         /// connect to this instance of the Chrome driver. Defaults to an empty string,
@@ -129,6 +140,11 @@ protected override string CommandLineArguments
                     argsBuilder.Append(" --verbose");
                 }
 
+                if (this.enableAppendLog)
+                {
+                    argsBuilder.Append(" --append-log");
+                }
+
                 if (!string.IsNullOrEmpty(this.logPath))
                 {
                     argsBuilder.AppendFormat(CultureInfo.InvariantCulture, " --log-path=\"{0}\"", this.logPath);