Use last frame processor to draw on debug surface view.

The last frame processor could use a different drawing command
than a four vertex triangle strip. So we need call its drawing
method again instead of assuming the shape.

PiperOrigin-RevId: 444217274

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

@@ -481,8 +481,7 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
       GlUtil.focusEglSurface(
       GlUtil.focusEglSurface(
           eglDisplay, eglContext, debugPreviewEglSurface, debugPreviewWidth, debugPreviewHeight);
           eglDisplay, eglContext, debugPreviewEglSurface, debugPreviewWidth, debugPreviewHeight);
       clearOutputFrame();
       clearOutputFrame();
-      // The four-vertex triangle strip forms a quad.
-      GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, /* first= */ 0, /* count= */ 4);
+      getLast(frameProcessors).drawFrame(presentationTimeUs);
       EGL14.eglSwapBuffers(eglDisplay, debugPreviewEglSurface);
       EGL14.eglSwapBuffers(eglDisplay, debugPreviewEglSurface);
     }
     }