fix missing cause of display refresh rate changing between…

fix missing cause of display refresh rate changing between videoframereleasetimehelper constructor and enable being called

library/core/src/main/java/com/google/android/exoplayer2/video/VideoFrameReleaseTimeHelper.java

@@ -74,7 +74,7 @@ public final class VideoFrameReleaseTimeHelper {
    */
    */
   public VideoFrameReleaseTimeHelper(Context context) {
   public VideoFrameReleaseTimeHelper(Context context) {
     this(getDefaultDisplayRefreshRate(context));
     this(getDefaultDisplayRefreshRate(context));
-    this.context = context;
+    this.context = context.getApplicationContext();
     registerDisplayListener();
     registerDisplayListener();
   }
   }
 
 
@@ -89,9 +89,10 @@ public final class VideoFrameReleaseTimeHelper {
     haveSync = false;
     haveSync = false;
     if (useDefaultDisplayVsync) {
     if (useDefaultDisplayVsync) {
       vsyncSampler.addObserver();
       vsyncSampler.addObserver();
-    }
+      setSync(getDefaultDisplayRefreshRate(context));
       registerDisplayListener();
       registerDisplayListener();
     }
     }
+  }
 
 
   /**
   /**
    * Disables the helper.
    * Disables the helper.