[dotnet] Add atlas textures to the our items included by default. (#9995)

dotnet/DefaultCompilationIncludes.md

@@ -33,6 +33,11 @@ All \*.jpg, \*.png and \*.json files inside asset catalogs (\*.xcassets) in
 the project directory or any subdirectory are included by default (as
 `ImageAsset` items).
 
+## Atlas Textures
+
+All \*.png files inside \*.atlas directories in the project directory or any
+subdirectory are included by default (as `AtlasTexture` items).
+
 ## Binding projects
 
 Default compilation includes is turned off for binding projects, because

dotnet/targets/Microsoft.Sdk.DefaultItems.template.props

@@ -47,4 +47,12 @@
 			<IsDefaultItem>true</IsDefaultItem>
 		</InterfaceDefinition>
 	</ItemGroup>
+
+	<!-- Default Atlas Texture file inclusion -->
+	<ItemGroup Condition="'$(TargetPlatformIdentifier)' == '@PLATFORM@' And '$(_EnableDefaultXamarinItems)' == 'true'">
+		<AtlasTexture Include="**\*.atlas\*.png">
+			<Link>$([MSBuild]::MakeRelative ('$(MSBuildProjectDirectory)', '%(Identity)'))</Link>
+			<IsDefaultItem>true</IsDefaultItem>
+		</AtlasTexture>
+	</ItemGroup>
 </Project>

tests/common/DotNet.cs

@@ -100,7 +100,6 @@ namespace Xamarin.Tests {
 						return false;
 
 					// There's a lot of TODOs here, those correspond with missing features in .NET and will be removed as those features are implemented
-					case ".png": // TODO
 					case ".metallib": // TODO
 						return false;
 					}
@@ -114,13 +113,6 @@ namespace Xamarin.Tests {
 						return false;
 					}
 
-					var dir = Path.GetDirectoryName (v);
-					var dirext = Path.GetExtension (dir);
-					switch (dirext) {
-					case ".atlasc": // TODO
-						return false;
-					}
-
 					var components = v.Split ('/');
 					if (components.Any (v => v.EndsWith (".framework", StringComparison.Ordinal))) {
 						return false; // TODO