Fix out-of-memory crashes on iOS when creating maps (#467)

* Pool map views on iOS 10 to avoid memory issues
Clean up disposal implementation for map renderer, delegate

* Enable 39489 test on iOS

* Add missing XF Maps references

* Add missing maps reference to Windows 8.1 project

* Actually enable the test for iOS

* Fix placement of Isolate override

* Don't create a new control for ImageRenderer if NewElement is null

* Reverting fixes to ViewRenderer Dispose; have to fix that in a separate PR

1 files changed, 31 insertions, 4 deletions

diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla39489.cs b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla39489.cs
index 3fe44681..0e04fcd5 100644
--- a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla39489.cs
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla39489.cs
@@ -2,6 +2,7 @@ using Xamarin.Forms.CustomAttributes;
 using Xamarin.Forms.Internals;
 using System.Threading;
 using System;
+using System.Diagnostics;
 using System.Threading.Tasks;
 using Xamarin.Forms.Maps;
 
@@ -13,7 +14,7 @@ using NUnit.Framework;
 namespace Xamarin.Forms.Controls.Issues
 {
 	[Preserve(AllMembers = true)]
-	[Issue(IssueTracker.Bugzilla, 39489, "Memory leak when using NavigationPage with Maps", PlatformAffected.Android)]
+	[Issue(IssueTracker.Bugzilla, 39489, "Memory leak when using NavigationPage with Maps", PlatformAffected.Android | PlatformAffected.iOS)]
 	public class Bugzilla39489 : TestNavigationPage
 	{
 		protected override void Init()
@@ -22,7 +23,6 @@ namespace Xamarin.Forms.Controls.Issues
 		}
 
 #if UITEST
-#if !__IOS__ // Temporarily disabling this test on iOS
 
 		protected override bool Isolate => true;
 
@@ -44,19 +44,40 @@ namespace Xamarin.Forms.Controls.Issues
 			}
 		}
 #endif
-#endif
+	}
+
+	public class Bz39489Map : Map
+	{
+		static int s_count;
+
+		public Bz39489Map()
+		{
+			Interlocked.Increment(ref s_count);
+			Debug.WriteLine($"++++++++ Bz39489Map : Constructor, count is {s_count}");
+		}
+
+		~Bz39489Map()
+		{
+			Interlocked.Decrement(ref s_count);
+			Debug.WriteLine($"-------- Bz39489Map: Destructor, count is {s_count}");
+		}
 	}
 
 	[Preserve(AllMembers = true)]
 	public class Bz39489Content : ContentPage
 	{
+		static int s_count;
+
 		public Bz39489Content()
 		{
+			Interlocked.Increment(ref s_count);
+			Debug.WriteLine($">>>>> Bz39489Content Bz39489Content 54: Constructor, count is {s_count}");
+
 			var button = new Button { Text = "New Page" };
 
 			var gcbutton = new Button { Text = "GC" };
 
-			var map = new Map();
+			var map = new Bz39489Map();
 
 			button.Clicked += Button_Clicked;
 			gcbutton.Clicked += GCbutton_Clicked;
@@ -76,5 +97,11 @@ namespace Xamarin.Forms.Controls.Issues
 		{
 			Navigation.PushAsync(new Bz39489Content());
 		}
+
+		~Bz39489Content()
+		{
+			Interlocked.Decrement(ref s_count);
+			Debug.WriteLine($">>>>> Bz39489Content ~Bz39489Content 82: Destructor, count is {s_count}");
+		}
 	}
 }
\ No newline at end of file