[FragmentItem] Fix LayoutText::HasTextBoxes

This fixes paint invalidation problem, because this function
is used in |LayoutObject::AdjustStyleDifference| to optimize
invalidations.

Fixes ~45 failures.

Bug: 982194
Change-Id: I2c749aed856bdbf8e06b2fb5c1f50b266a68efb9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2022444
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735337}

third_party/blink/renderer/core/layout/layout_text.cc

@@ -415,9 +415,12 @@ Vector<LayoutText::TextBoxInfo> LayoutText::GetTextBoxInfo() const {
 
 bool LayoutText::HasTextBoxes() const {
   if (RuntimeEnabledFeatures::LayoutNGEnabled()) {
-    auto fragments = NGPaintFragment::InlineFragmentsFor(this);
-    if (fragments.IsInLayoutNGInlineFormattingContext())
-      return !(fragments.begin() == fragments.end());
+    if (IsInLayoutNGInlineFormattingContext()) {
+      NGInlineCursor cursor;
+      cursor.MoveTo(*this);
+      return cursor.IsNotNull();
+    }
+
     // When legacy is forced, IsInLayoutNGInlineFormattingContext is false,
     // and we fall back to normal HasTextBox
     return FirstTextBox();