[coregraphics] Expose CGColor.CreateByMatchingToColorSpace (#10223)

and add unit test

Fix https://github.com/xamarin/xamarin-macios/issues/10212

src/CoreGraphics/CGColor.cs

@@ -278,7 +278,8 @@ namespace CoreGraphics {
 			/* __nullable CGColorSpaceRef* */ IntPtr space, CGColorRenderingIntent intent,
 			/* CGColorRef __nullable */ IntPtr color, /* __nullable CFDictionaryRef */ IntPtr options);
 
-		static CGColor CreateByMatchingToColorSpace (CGColorSpace space, CGColorRenderingIntent intent,
+		[iOS (9,0)][Mac (10,11)]
+		static public CGColor CreateByMatchingToColorSpace (CGColorSpace space, CGColorRenderingIntent intent,
 			CGColor color, NSDictionary options)
 		{
 			var h = CGColorCreateCopyByMatchingToColorSpace (space == null ? IntPtr.Zero : space.Handle, intent,

tests/monotouch-test/CoreGraphics/ColorTest.cs

@@ -107,6 +107,21 @@ namespace MonoTouchFixtures.CoreGraphics {
 			}
 		}
 
+		[Test]
+		public void CreateByMatchingToColorSpace ()
+		{
+			TestRuntime.AssertXcodeVersion (8, 0);
+			using (var c = CGColor.CreateByMatchingToColorSpace (null, CGColorRenderingIntent.Default, null, null)) {
+				Assert.IsNull (c, "0");
+			}
+
+			using (var cs = CGColorSpace.CreateGenericRgbLinear ())
+			using (var c1 = CGColor.CreateSrgb (1, 2, 3, 4))
+			using (var c2 = CGColor.CreateByMatchingToColorSpace (cs, CGColorRenderingIntent.Default, c1, null)) {
+				Assert.IsNotNull (c1, "1");
+				Assert.IsNotNull (c2, "2");
+			}
+		}
 	}
 }