Add failing test for storyboard start time ordering

osu.Game.Tests/Beatmaps/Formats/LegacyStoryboardDecoderTest.cs

@@ -95,6 +95,26 @@ namespace osu.Game.Tests.Beatmaps.Formats
             }
         }
 
+        [Test]
+        public void TestOutOfOrderStartTimes()
+        {
+            var decoder = new LegacyStoryboardDecoder();
+
+            using (var resStream = TestResources.OpenResource("out-of-order-starttimes.osb"))
+            using (var stream = new LineBufferedReader(resStream))
+            {
+                var storyboard = decoder.Decode(stream);
+
+                StoryboardLayer background = storyboard.Layers.Single(l => l.Depth == 3);
+                Assert.AreEqual(2, background.Elements.Count);
+
+                Assert.AreEqual(1500, background.Elements[0].StartTime);
+                Assert.AreEqual(1000, background.Elements[1].StartTime);
+
+                Assert.AreEqual(1000, storyboard.FirstEventTime);
+            }
+        }
+
         [Test]
         public void TestDecodeVariableWithSuffix()
         {

osu.Game.Tests/Resources/out-of-order-starttimes.osb

@@ -0,0 +1,6 @@
+[Events]
+//Storyboard Layer 0 (Background)
+Sprite,Background,TopCentre,"img.jpg",320,240
+ F,0,1500,1600,0,1
+Sprite,Background,TopCentre,"img.jpg",320,240
+ F,0,1000,1100,0,1