Adding option to not delete anonymous Firefox profile in .NET

This change adds an option to the .NET FirefoxProfile class so that the
driver will not delete the anonymous profile created by the driver. Since
the driver cannot and should not use an existing profile in situ because
of the multiple instance automation case, this change means that
modifications applied to the anonymous profile can be retained and
used in future anonymous profiles.The implication is that the user can
now make modifications to a profile, and retain those profile modifications
(e.g., cookies) into other future profiles, simulating persistent changes
over multiple browser launches. Fixes issue SeleniumHQ#7374.

dotnet/src/webdriver/Firefox/FirefoxProfile.cs

@@ -55,6 +55,7 @@ public class FirefoxProfile
         private bool acceptUntrustedCerts;
         private bool assumeUntrustedIssuer;
         private bool deleteSource;
+        private bool deleteOnClean = true;
         private Preferences profilePreferences;
         private Dictionary<string, FirefoxExtension> extensions = new Dictionary<string, FirefoxExtension>();
         #endregion
@@ -116,6 +117,16 @@ public string ProfileDirectory
             get { return this.profileDir; }
         }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether to delete this profile after use with
+        /// the <see cref="FirefoxDriver"/>.
+        /// </summary>
+        public bool DeleteAfterUse
+        {
+            get { return this.deleteOnClean; }
+            set { this.deleteOnClean = value; }
+        }
+
         /// <summary>
         /// Gets or sets a value indicating whether native events are enabled.
         /// </summary>
@@ -303,7 +314,7 @@ public void WriteToDisk()
         /// is deleted.</remarks>
         public void Clean()
         {
-            if (!string.IsNullOrEmpty(this.profileDir) && Directory.Exists(this.profileDir))
+            if (this.deleteOnClean && !string.IsNullOrEmpty(this.profileDir) && Directory.Exists(this.profileDir))
             {
                 FileUtilities.DeleteDirectory(this.profileDir);
             }