Add nanoTime method to Clock to support overriding System.nanoTime()

#minor-release

PiperOrigin-RevId: 545237925

RELEASENOTES.md

@@ -102,6 +102,8 @@
     *   Make `TestExoPlayerBuilder` and `FakeClock` compatible with Espresso UI
         tests and Compose UI tests. This fixes a bug where playback advances
         non-deterministically during Espresso or Compose view interactions.
+    *   Add a `nanoTime()` method to `Clock` to provide override support of
+        `System.nanoTime()`
 *   Remove deprecated symbols:
     *   Remove
         `TransformationRequest.Builder.setEnableRequestSdrToneMapping(boolean)`

libraries/common/src/main/java/androidx/media3/common/util/Clock.java

@@ -46,6 +46,9 @@ public interface Clock {
    */
   long uptimeMillis();
 
+  /** See {@link java.lang.System#nanoTime()} */
+  long nanoTime();
+
   /**
    * Creates a {@link HandlerWrapper} using a specified looper and a specified callback for handling
    * messages.

libraries/common/src/main/java/androidx/media3/common/util/SystemClock.java

@@ -44,6 +44,11 @@ public class SystemClock implements Clock {
     return android.os.SystemClock.uptimeMillis();
   }
 
+  @Override
+  public long nanoTime() {
+    return System.nanoTime();
+  }
+
   @Override
   public HandlerWrapper createHandler(Looper looper, @Nullable Callback callback) {
     return new SystemHandlerWrapper(new Handler(looper, callback));

libraries/test_utils/src/main/java/androidx/media3/test/utils/FakeClock.java

@@ -159,6 +159,12 @@ public class FakeClock implements Clock {
     return timeSinceBootMs;
   }
 
+  @Override
+  public synchronized long nanoTime() {
+    // Milliseconds to nanoseconds
+    return timeSinceBootMs * 1000000L;
+  }
+
   @Override
   public long uptimeMillis() {
     return elapsedRealtime();