Check wether a chart is populated; Fixes to graph's colour setting

osu.Game/Online/API/Requests/GetChangelogChartRequest.cs

@@ -0,0 +1,21 @@
+// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using osu.Game.Online.API.Requests.Responses;
+using System.Collections.Generic;
+
+namespace osu.Game.Online.API.Requests
+{
+    public class GetChangelogChartRequest : APIRequest<APIChangelogChart>
+    {
+        private readonly string updateStream;
+
+        public GetChangelogChartRequest() => updateStream = null;
+
+        public GetChangelogChartRequest(string updateStreamName) => updateStream = updateStreamName;
+
+        protected override string Target => $@"changelog/{(!string.IsNullOrEmpty(updateStream) ?
+            updateStream + "/" : "")}chart-config";
+        protected override string Uri => $@"https://houtarouoreki.github.io/fake-api/{Target}"; // for testing
+    }
+}

osu.Game/Online/API/Requests/Responses/APIChangelogChart.cs

@@ -0,0 +1,34 @@
+// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using Newtonsoft.Json;
+using osu.Framework.Lists;
+using System;
+using System.Collections.Generic;
+
+namespace osu.Game.Online.API.Requests.Responses
+{
+    public class APIChangelogChart
+    {
+        [JsonProperty("build_history")]
+        public List<BuildHistory> BuildHistory { get; set; }
+
+        [JsonProperty("order")]
+        public List<string> Order { get; set; }
+
+        [JsonProperty("stream_name")]
+        public string StreamName { get; set; }
+    }
+
+    public class BuildHistory
+    {
+        [JsonProperty("created_at")]
+        public DateTimeOffset CreatedAt { get; set; }
+
+        [JsonProperty("user_count")]
+        public long UserCount { get; set; }
+
+        [JsonProperty("label")]
+        public string Label { get; set; }
+    }
+}