https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/paint/TextPainter.cpp?l=260

TextPainter always creates a new TextRunPaintInfo with an empty cachedTextBlob so getTextIntercepts in Font.cpp does not need the following block:

  if (runInfo.cachedTextBlob && runInfo.cachedTextBlob->get()) {
    SkScalar boundsArray[2] = {std::get<0>(bounds), std::get<1>(bounds)};
    int numIntervals = paint.getTextBlobIntercepts(
        runInfo.cachedTextBlob->get(), boundsArray, nullptr);
    if (!numIntervals)
      return;
    DCHECK_EQ(numIntervals % 2, 0);
    intercepts.resize(numIntervals / 2);
    paint.getTextBlobIntercepts(runInfo.cachedTextBlob->get(), boundsArray,
                                reinterpret_cast<SkScalar*>(intercepts.data()));
    return;
  }