Misc refactoring.

Use @VisibleForTesting and add some comments for GL code.

Refactoring change only. No functional changes intended

PiperOrigin-RevId: 412428196

library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecUtil.java

@@ -27,6 +27,7 @@ import androidx.annotation.CheckResult;
 import androidx.annotation.GuardedBy;
 import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
+import androidx.annotation.VisibleForTesting;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.util.Log;
@@ -105,11 +106,8 @@ public final class MediaCodecUtil {
     }
   }
 
-  /**
-   * Clears the codec cache.
-   *
-   * <p>This method should only be called in tests.
-   */
+  /* Clears the codec cache.*/
+  @VisibleForTesting
   public static synchronized void clearDecoderInfoCache() {
     decoderInfosCache.clear();
   }

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

@@ -176,7 +176,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     checkGlError();
 
     // Render.
-    GLES20.glDrawArrays(meshData.drawMode, 0, meshData.vertexCount);
+    GLES20.glDrawArrays(meshData.drawMode, /* first= */ 0, meshData.vertexCount);
     checkGlError();
 
     GLES20.glDisableVertexAttribArray(positionHandle);

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/FrameEditor.java

@@ -143,7 +143,7 @@ import java.io.IOException;
     inputSurfaceTexture.getTransformMatrix(textureTransformMatrix);
     copyProgram.setFloatsUniform("tex_transform", textureTransformMatrix);
     copyProgram.bindAttributesAndUniforms();
-    GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
+    GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, /* first= */ 0, /* count= */ 4);
     long surfaceTextureTimestampNs = inputSurfaceTexture.getTimestamp();
     EGLExt.eglPresentationTimeANDROID(eglDisplay, eglSurface, surfaceTextureTimestampNs);
     EGL14.eglSwapBuffers(eglDisplay, eglSurface);