Move DebugTextViewHelper to core

It's closely tied to SimpleExoPlayer, so cannot be part of a UI module
that depends only on common.

PiperOrigin-RevId: 357085802

RELEASENOTES.md

@@ -31,6 +31,8 @@
     *   Only release 'keepalive' references to `DrmSession` in
         `DefaultDrmSessionManager#release()` if keepalive is enabled
         ([#8576](https://github.com/google/ExoPlayer/issues/8576)).
+*   Library restructuring:
+    *   `DebugTextViewHelper` moved from `ui` package to `util` package.
 *   Remove deprecated symbols:
     *   Remove `Player.DefaultEventListener`. Use `Player.EventListener`
         instead.

demos/main/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java

@@ -51,10 +51,10 @@ import com.google.android.exoplayer2.source.ads.AdsLoader;
 import com.google.android.exoplayer2.trackselection.DefaultTrackSelector;
 import com.google.android.exoplayer2.trackselection.MappingTrackSelector.MappedTrackInfo;
 import com.google.android.exoplayer2.trackselection.TrackSelectionArray;
-import com.google.android.exoplayer2.ui.DebugTextViewHelper;
 import com.google.android.exoplayer2.ui.StyledPlayerControlView;
 import com.google.android.exoplayer2.ui.StyledPlayerView;
 import com.google.android.exoplayer2.upstream.DataSource;
+import com.google.android.exoplayer2.util.DebugTextViewHelper;
 import com.google.android.exoplayer2.util.ErrorMessageProvider;
 import com.google.android.exoplayer2.util.EventLogger;
 import com.google.android.exoplayer2.util.Util;

library/ui/src/main/java/com/google/android/exoplayer2/ui/DebugTextViewHelper.java → library/core/src/main/java/com/google/android/exoplayer2/util/DebugTextViewHelper.java

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package com.google.android.exoplayer2.ui;
+package com.google.android.exoplayer2.util;
 
 import android.annotation.SuppressLint;
 import android.os.Looper;
@@ -22,7 +22,6 @@ import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.SimpleExoPlayer;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
-import com.google.android.exoplayer2.util.Assertions;
 import java.util.Locale;
 
 /**