Make core Ticker abstract and public (#116)

* Make core Ticker abstract and public
Make the core Ticker abstract and public so it can be inherited by platform
implementations; remove now-unused parts of original Ticker; add CreateTicker
to IPlatformServices; remove unused CreateTimer methods from IPlatformServices

* Add docs for Ticker

* Remove unnecessary Ticker.Default set

* Move Ticker into Internals

* Update Ticker docs

* Remove old Ticker docs

* Remove commented code

4 files changed, 34 insertions, 4 deletions

diff --git a/Xamarin.Forms.Core.UnitTests/MockPlatformServices.cs b/Xamarin.Forms.Core.UnitTests/MockPlatformServices.cs
index 7d2317b3..5109cbb4 100644
--- a/Xamarin.Forms.Core.UnitTests/MockPlatformServices.cs
+++ b/Xamarin.Forms.Core.UnitTests/MockPlatformServices.cs
@@ -9,6 +9,8 @@ using Xamarin.Forms;
 using Xamarin.Forms.Core.UnitTests;
 using System.Security.Cryptography;
 using System.Text;
+using Xamarin.Forms.Internals;
+
 #if WINDOWS_PHONE
 using Xamarin.Forms.Platform.WinPhone;
 #endif
@@ -88,6 +90,11 @@ namespace Xamarin.Forms.Core.UnitTests
 				invokeOnMainThread (action);
 		}
 
+		public Ticker CreateTicker()
+		{
+			return new MockTicker();
+		}
+
 		public void StartTimer (TimeSpan interval, Func<bool> callback)
 		{
 			Timer timer = null;
@@ -267,4 +274,24 @@ namespace Xamarin.Forms.Core.UnitTests
 		{
 		}
 	}
+
+	internal class MockTicker : Ticker
+	{
+		bool _enabled;
+
+		protected override void EnableTimer()
+		{
+			_enabled = true;
+
+			while (_enabled)
+			{
+				SendSignals(16);
+			}
+		}
+
+		protected override void DisableTimer()
+		{
+			_enabled = false;
+		}
+	}
 }
\ No newline at end of file
diff --git a/Xamarin.Forms.Core.UnitTests/MotionTests.cs b/Xamarin.Forms.Core.UnitTests/MotionTests.cs
index acb764d7..0d8d476c 100644
--- a/Xamarin.Forms.Core.UnitTests/MotionTests.cs
+++ b/Xamarin.Forms.Core.UnitTests/MotionTests.cs
@@ -1,25 +1,26 @@
 using System;
 using System.Collections.Generic;
 using NUnit.Framework;
+using Xamarin.Forms.Internals;
 
 namespace Xamarin.Forms.Core.UnitTests
 {
 	internal class BlockingTicker : Ticker
 	{
-		bool enabled;
+		bool _enabled;
 
 		protected override void EnableTimer ()
 		{
-			enabled = true;
+			_enabled = true;
 
-			while (enabled) {
+			while (_enabled) {
 				SendSignals (16);
 			}
 		}
 
 		protected override void DisableTimer ()
 		{
-			enabled = false;
+			_enabled = false;
 		}
 	}
 
diff --git a/Xamarin.Forms.Core.UnitTests/ProgressBarTests.cs b/Xamarin.Forms.Core.UnitTests/ProgressBarTests.cs
index 2af7eac0..1192b7e7 100644
--- a/Xamarin.Forms.Core.UnitTests/ProgressBarTests.cs
+++ b/Xamarin.Forms.Core.UnitTests/ProgressBarTests.cs
@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 
 using NUnit.Framework;
+using Xamarin.Forms.Internals;
 
 namespace Xamarin.Forms.Core.UnitTests
 {
diff --git a/Xamarin.Forms.Core.UnitTests/ViewUnitTests.cs b/Xamarin.Forms.Core.UnitTests/ViewUnitTests.cs
index 97700ca4..9e7f0546 100644
--- a/Xamarin.Forms.Core.UnitTests/ViewUnitTests.cs
+++ b/Xamarin.Forms.Core.UnitTests/ViewUnitTests.cs
@@ -4,6 +4,7 @@ using System.Collections.Specialized;
 using System.Threading.Tasks;
 
 using NUnit.Framework;
+using Xamarin.Forms.Internals;
 
 namespace Xamarin.Forms.Core.UnitTests
 {