test: run UpdateRenderCachePNGInStreamingAssets() test in Windows and Mac only (#460)

* ignore tests on Linux (failing)

Author: sindharta

Tests/Editor/Scripts/RenderCachePlayableAssetTest.cs

@@ -3,6 +3,7 @@
 using NUnit.Framework;
 using Unity.EditorCoroutines.Editor;
 using Unity.FilmInternalUtilities;
+using Unity.FilmInternalUtilities.Editor;
 using UnityEngine;
 using UnityEngine.Playables;
 using Unity.StreamingImageSequence.Editor;
@@ -32,6 +33,7 @@ public IEnumerator CreatePlayableAsset() {
 
 //----------------------------------------------------------------------------------------------------------------------                
     [UnityTest]
+    [UnityPlatform(RuntimePlatform.OSXEditor, RuntimePlatform.WindowsEditor)]
     public IEnumerator UpdateRenderCachePNGInStreamingAssets() {
         PlayableDirector director   = EditorUtilityTest.NewSceneWithDirector();
         TimelineClip     clip       = EditorUtilityTest.CreateTestRenderCacheTimelineClip(director);
@@ -58,25 +60,21 @@ public IEnumerator UpdateRenderCachePNGInStreamingAssets() {
         //Update RenderCache              
         EditorCoroutineUtility.StartCoroutineOwnerless(
             RenderCachePlayableAssetInspector.UpdateRenderCacheCoroutine(director, renderCachePlayableAsset)
-        );        
+        );
+
+        Assert.IsTrue(Directory.Exists(OUTPUT_FOLDER));
 
         //A hack to wait until the coroutine is finished
-        const float TIMEOUT_SEC = 3.0f;
-        Assert.IsTrue(Directory.Exists(OUTPUT_FOLDER));
-        float  prevTime      = Time.realtimeSinceStartup;        
-        while (Time.realtimeSinceStartup - prevTime < TIMEOUT_SEC) {
-             yield return null;
-        }       
+        const int TIMEOUT_FRAMES = 60 * 3;
+        yield return YieldEditorUtility.WaitForFramesAndIncrementUndo(TIMEOUT_FRAMES);
+        
 
         string imageFilePath = renderCachePlayableAsset.GetImageFilePath(0);
         Assert.IsTrue(File.Exists(imageFilePath));
         ImageLoader.RequestLoadFullImage(imageFilePath);
 
         //Another hack to wait until the load is finished
-        prevTime = Time.realtimeSinceStartup;
-        while (Time.realtimeSinceStartup - prevTime < TIMEOUT_SEC) {
-            yield return null;
-        }       
+        yield return YieldEditorUtility.WaitForFramesAndIncrementUndo(TIMEOUT_FRAMES);
 
         ImageLoader.GetImageDataInto(imageFilePath,StreamingImageSequenceConstants.IMAGE_TYPE_FULL,out ImageData imageData);
         Assert.AreEqual(StreamingImageSequenceConstants.READ_STATUS_SUCCESS, imageData.ReadStatus);