Update reflection cubemap inspector

ScriptableRenderPipeline/HDRenderPipeline/Editor/Lighting/HDReflectionProbeEditor.Drawers.cs

             GUILayout.FlexibleSpace();
             EditorGUILayout.EndHorizontal();
         }
-        //static void OnBakeCustomButton(object data)
-        //{
-        //    var mode = (int)data;
-
-        //    var p = target as ReflectionProbe;
-        //    if (mode == 0)
-        //        BakeCustomReflectionProbe(p, false, true);
-        //}
 
         #region Influence Volume
         static void Drawer_InfluenceBoxSettings(UIState s, SerializedReflectionProbe p, Editor owner)

ScriptableRenderPipeline/HDRenderPipeline/Editor/Lighting/HDReflectionProbeEditor.Preview.cs

+using UnityEngine;
+
+namespace UnityEditor.Experimental.Rendering
+{
+    partial class HDReflectionProbeEditor
+    {
+        HDCubemapInspector m_CubemapEditor;
+
+        public override bool HasPreviewGUI()
+        {
+            if (targets.Length > 1)
+                return false;  // We only handle one preview for reflection probes
+
+            // Ensure valid cube map editor (if possible)
+            if (ValidPreviewSetup())
+            {
+                Editor editor = m_CubemapEditor;
+                CreateCachedEditor(((ReflectionProbe)target).texture, null, ref editor);
+                m_CubemapEditor = editor as HDCubemapInspector;
+            }
+
+            // If having one probe selected we always want preview (to prevent preview window from popping)
+            return true;
+        }
+
+        public override void OnPreviewSettings()
+        {
+            if (!ValidPreviewSetup()
+                || m_CubemapEditor == null)
+                return;
+
+            m_CubemapEditor.OnPreviewSettings();
+        }
+
+        public override void OnPreviewGUI(Rect position, GUIStyle style)
+        {
+            if (!ValidPreviewSetup()
+                || m_CubemapEditor == null)
+            {
+                GUILayout.BeginHorizontal();
+                GUILayout.FlexibleSpace();
+                Color prevColor = GUI.color;
+                GUI.color = new Color(1, 1, 1, 0.5f);
+                GUILayout.Label("Reflection Probe not baked yet");
+                GUI.color = prevColor;
+                GUILayout.FlexibleSpace();
+                GUILayout.EndHorizontal();
+                return;
+            }
+
+            var p = target as ReflectionProbe;
+            if (p != null && p.texture != null && targets.Length == 1)
+                m_CubemapEditor.DrawPreview(position);
+
+        }
+
+        bool ValidPreviewSetup()
+        {
+            var p = target as ReflectionProbe;
+            return p != null && p.texture != null;
+        }
+    }
+}

ScriptableRenderPipeline/HDRenderPipeline/Editor/Lighting/HDReflectionProbeEditor.Preview.cs.meta

+fileFormatVersion: 2
+guid: 10da9cb15a7644245b87056613737840
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: