Move DumpableBox into test-util module

We need to use this class in muxer's robolectric and instrumentation tests, hence moving it to test-util module.

PiperOrigin-RevId: 512047605

testutils/src/main/java/com/google/android/exoplayer2/testutil/DumpableMp4Box.java

+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.testutil;
+
+import com.google.android.exoplayer2.util.Assertions;
+import com.google.android.exoplayer2.util.ParsableByteArray;
+import com.google.common.collect.ImmutableSet;
+import java.nio.ByteBuffer;
+
+/** Wraps an Mp4 box to allow dumping it. */
+public final class DumpableMp4Box implements Dumper.Dumpable {
+  private static final ImmutableSet<String> CONTAINER_BOXES =
+      ImmutableSet.of("moov", "trak", "mdia", "minf", "stbl", "edts", "meta");
+  private final ParsableByteArray box;
+
+  /***
+   * Creates an instance.
+   *
+   * @param box The Mp4 box to wrap.
+   */
+  public DumpableMp4Box(ByteBuffer box) {
+    this.box = new ParsableByteArray(box.array());
+  }
+
+  @Override
+  public void dump(Dumper dumper) {
+    dumpBoxRecursively(box.limit(), dumper);
+  }
+
+  private void dumpBoxRecursively(long endPosition, Dumper dumper) {
+    while (box.getPosition() < endPosition) {
+      long size = box.readInt();
+      String name = box.readString(/* length= */ 4);
+      long payloadSize = size - 8;
+      // When the box needs 64-bit box size (typically used for mdat box), then the original 32-bit
+      // box size is set to 1.
+      if (size == 1) {
+        size = box.readUnsignedLongToLong();
+        // Parsing is not supported for box having size > Integer.MAX_VALUE.
+        Assertions.checkState(size <= Integer.MAX_VALUE);
+        // Subtract 4 bytes (32-bit box size) + 4 bytes (box name) + 8 bytes (64-bit box size).
+        payloadSize = size - 16;
+      }
+      dumper.startBlock(name + " (" + size + " bytes)");
+      if (CONTAINER_BOXES.contains(name)) {
+        dumpBoxRecursively(box.getPosition() + payloadSize, dumper);
+      } else {
+        byte[] data = new byte[(int) payloadSize];
+        box.readBytes(data, /* offset= */ 0, (int) payloadSize);
+        dumper.add("Data", data);
+      }
+      dumper.endBlock();
+    }
+  }
+}