SendAsync returns correct result type

.. so user does not have to use cast on every command result that
returns something interesting

source/ChromeDevTools/ChromeSession.cs

@@ -81,10 +81,23 @@ namespace MasterDevs.ChromeDevTools
             return SendCommand(command, cancellationToken);
         }
 
-        public Task<ICommandResponse> SendAsync<T>(T parameter, CancellationToken cancellationToken)
+        public Task<CommandResponse<T>> SendAsync<T>(ICommand<T> parameter, CancellationToken cancellationToken)
         {
             var command = _commandFactory.Create(parameter);
-            return SendCommand(command, cancellationToken);
+            var task = SendCommand(command, cancellationToken);
+            return CastTaskResult<ICommandResponse, CommandResponse<T>>(task);
+        }
+
+        private Task<TDerived> CastTaskResult<TBase, TDerived>(Task<TBase> task) where TDerived: TBase
+        {
+            var tcs = new TaskCompletionSource<TDerived>();
+            task.ContinueWith(t => tcs.SetResult((TDerived)t.Result),
+                TaskContinuationOptions.OnlyOnRanToCompletion);
+            task.ContinueWith(t => tcs.SetException(t.Exception.InnerExceptions),
+                TaskContinuationOptions.OnlyOnFaulted);
+            task.ContinueWith(t => tcs.SetCanceled(),
+                TaskContinuationOptions.OnlyOnCanceled);
+            return tcs.Task;
         }
 
         public void Subscribe<T>(Action<T> handler) where T : class

source/ChromeDevTools/ChromeSessionExtensions.cs

@@ -5,9 +5,9 @@ namespace MasterDevs.ChromeDevTools
 {
     public static class ChromeSessionExtensions
     {
-        public static Task<ICommandResponse> SendAsync<T>(this IChromeSession session, T parameter)
+        public static Task<CommandResponse<T>> SendAsync<T>(this IChromeSession session, ICommand<T> parameter)
         {
-            return session.SendAsync<T>(parameter, CancellationToken.None);
+            return session.SendAsync(parameter, CancellationToken.None);
         }
 
         public static Task<ICommandResponse> SendAsync<T>(this IChromeSession session)

source/ChromeDevTools/IChromeSession.cs

@@ -4,9 +4,13 @@ using System.Threading.Tasks;
 
 namespace MasterDevs.ChromeDevTools
 {
+    public interface ICommand<T>
+    {
+
+    }
     public interface IChromeSession
     {
-        Task<ICommandResponse> SendAsync<T>(T parameter, CancellationToken cancellationToken);
+        Task<CommandResponse<TResponse>> SendAsync<TResponse>(ICommand<TResponse> parameter, CancellationToken cancellationToken);
 
         Task<ICommandResponse> SendAsync<T>(CancellationToken cancellationToken);
 

source/ChromeDevTools/Protocol/Chrome/Accessibility/GetPartialAXTreeCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Accessibility
 	/// </summary>
 	[Command(ProtocolName.Accessibility.GetPartialAXTree)]
 	[SupportedBy("Chrome")]
-	public class GetPartialAXTreeCommand
+	public class GetPartialAXTreeCommand: ICommand<GetPartialAXTreeCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets ID of node to get the partial accessibility tree for.

source/ChromeDevTools/Protocol/Chrome/Animation/DisableCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Animation
 	/// </summary>
 	[Command(ProtocolName.Animation.Disable)]
 	[SupportedBy("Chrome")]
-	public class DisableCommand
+	public class DisableCommand: ICommand<DisableCommandResponse>
 	{
 	}
 }

source/ChromeDevTools/Protocol/Chrome/Animation/EnableCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Animation
 	/// </summary>
 	[Command(ProtocolName.Animation.Enable)]
 	[SupportedBy("Chrome")]
-	public class EnableCommand
+	public class EnableCommand: ICommand<EnableCommandResponse>
 	{
 	}
 }

source/ChromeDevTools/Protocol/Chrome/Animation/GetCurrentTimeCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Animation
 	/// </summary>
 	[Command(ProtocolName.Animation.GetCurrentTime)]
 	[SupportedBy("Chrome")]
-	public class GetCurrentTimeCommand
+	public class GetCurrentTimeCommand: ICommand<GetCurrentTimeCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets Id of animation.

source/ChromeDevTools/Protocol/Chrome/Animation/GetPlaybackRateCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Animation
 	/// </summary>
 	[Command(ProtocolName.Animation.GetPlaybackRate)]
 	[SupportedBy("Chrome")]
-	public class GetPlaybackRateCommand
+	public class GetPlaybackRateCommand: ICommand<GetPlaybackRateCommandResponse>
 	{
 	}
 }

source/ChromeDevTools/Protocol/Chrome/Animation/ReleaseAnimationsCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Animation
 	/// </summary>
 	[Command(ProtocolName.Animation.ReleaseAnimations)]
 	[SupportedBy("Chrome")]
-	public class ReleaseAnimationsCommand
+	public class ReleaseAnimationsCommand: ICommand<ReleaseAnimationsCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets List of animation ids to seek.

source/ChromeDevTools/Protocol/Chrome/Animation/ResolveAnimationCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Animation
 	/// </summary>
 	[Command(ProtocolName.Animation.ResolveAnimation)]
 	[SupportedBy("Chrome")]
-	public class ResolveAnimationCommand
+	public class ResolveAnimationCommand: ICommand<ResolveAnimationCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets Animation id.

source/ChromeDevTools/Protocol/Chrome/Animation/SeekAnimationsCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Animation
 	/// </summary>
 	[Command(ProtocolName.Animation.SeekAnimations)]
 	[SupportedBy("Chrome")]
-	public class SeekAnimationsCommand
+	public class SeekAnimationsCommand: ICommand<SeekAnimationsCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets List of animation ids to seek.

source/ChromeDevTools/Protocol/Chrome/Animation/SetPausedCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Animation
 	/// </summary>
 	[Command(ProtocolName.Animation.SetPaused)]
 	[SupportedBy("Chrome")]
-	public class SetPausedCommand
+	public class SetPausedCommand: ICommand<SetPausedCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets Animations to set the pause state of.

source/ChromeDevTools/Protocol/Chrome/Animation/SetPlaybackRateCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Animation
 	/// </summary>
 	[Command(ProtocolName.Animation.SetPlaybackRate)]
 	[SupportedBy("Chrome")]
-	public class SetPlaybackRateCommand
+	public class SetPlaybackRateCommand: ICommand<SetPlaybackRateCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets Playback rate for animations on page

source/ChromeDevTools/Protocol/Chrome/Animation/SetTimingCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Animation
 	/// </summary>
 	[Command(ProtocolName.Animation.SetTiming)]
 	[SupportedBy("Chrome")]
-	public class SetTimingCommand
+	public class SetTimingCommand: ICommand<SetTimingCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets Animation id.

source/ChromeDevTools/Protocol/Chrome/ApplicationCache/EnableCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.ApplicationCache
 	/// </summary>
 	[Command(ProtocolName.ApplicationCache.Enable)]
 	[SupportedBy("Chrome")]
-	public class EnableCommand
+	public class EnableCommand: ICommand<EnableCommandResponse>
 	{
 	}
 }

source/ChromeDevTools/Protocol/Chrome/ApplicationCache/GetApplicationCacheForFrameCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.ApplicationCache
 	/// </summary>
 	[Command(ProtocolName.ApplicationCache.GetApplicationCacheForFrame)]
 	[SupportedBy("Chrome")]
-	public class GetApplicationCacheForFrameCommand
+	public class GetApplicationCacheForFrameCommand: ICommand<GetApplicationCacheForFrameCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets Identifier of the frame containing document whose application cache is retrieved.

source/ChromeDevTools/Protocol/Chrome/ApplicationCache/GetFramesWithManifestsCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.ApplicationCache
 	/// </summary>
 	[Command(ProtocolName.ApplicationCache.GetFramesWithManifests)]
 	[SupportedBy("Chrome")]
-	public class GetFramesWithManifestsCommand
+	public class GetFramesWithManifestsCommand: ICommand<GetFramesWithManifestsCommandResponse>
 	{
 	}
 }

source/ChromeDevTools/Protocol/Chrome/ApplicationCache/GetManifestForFrameCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.ApplicationCache
 	/// </summary>
 	[Command(ProtocolName.ApplicationCache.GetManifestForFrame)]
 	[SupportedBy("Chrome")]
-	public class GetManifestForFrameCommand
+	public class GetManifestForFrameCommand: ICommand<GetManifestForFrameCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets Identifier of the frame containing document whose manifest is retrieved.

source/ChromeDevTools/Protocol/Chrome/Browser/GetWindowBoundsCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Browser
 	/// </summary>
 	[Command(ProtocolName.Browser.GetWindowBounds)]
 	[SupportedBy("Chrome")]
-	public class GetWindowBoundsCommand
+	public class GetWindowBoundsCommand: ICommand<GetWindowBoundsCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets Browser window id.

source/ChromeDevTools/Protocol/Chrome/Browser/GetWindowForTargetCommand.cs

@@ -9,7 +9,7 @@ namespace MasterDevs.ChromeDevTools.Protocol.Chrome.Browser
 	/// </summary>
 	[Command(ProtocolName.Browser.GetWindowForTarget)]
 	[SupportedBy("Chrome")]
-	public class GetWindowForTargetCommand
+	public class GetWindowForTargetCommand: ICommand<GetWindowForTargetCommandResponse>
 	{
 		/// <summary>
 		/// Gets or sets Devtools agent host id.