[LayoutNG] Fix paint invalidation of LayoutText

Root cause of missing invalidations:
LayoutObject::AdjustStyleDifference was not marking LayoutText with NG rendering
as NeedPaintInvalidation. This caused invalidation not to propagate to document.
It was not marked because
LayoutObject:1789 ToLayoutText(this)->HasTextBoxes() always returned false for NG.

The fix was to make HasTextBoxes() NG-aware. This caused 2 callers
of HasTextBoxes() to behave incorrectly. Created HasLegacyTextBoxes(),
and added a TODO to remove them.

Bug: 819372
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: If2c4ddc0c9c707d11bb9115ef26ac578387c8359
Reviewed-on: https://chromium-review.googlesource.com/961526
Commit-Queue: Aleks Totic <atotic@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543885}

third_party/WebKit/Source/core/layout/LayoutText.cpp

@@ -306,12 +306,25 @@ void LayoutText::DeleteTextBoxes() {
 
 Optional<FloatPoint> LayoutText::GetUpperLeftCorner() const {
   DCHECK(!IsBR());
-  if (!HasTextBoxes())
+  // TODO(layoutng) Implement GetUpperLeftCorner for layoutng
+  if (!HasLegacyTextBoxes())
     return WTF::nullopt;
   return FloatPoint(LinesBoundingBox().X(),
                     FirstTextBox()->Root().LineTop().ToFloat());
 }
 
+bool LayoutText::HasTextBoxes() const {
+  if (RuntimeEnabledFeatures::LayoutNGEnabled()) {
+    auto fragments = NGPaintFragment::InlineFragmentsFor(this);
+    if (fragments.IsInLayoutNGInlineFormattingContext())
+      return !(fragments.begin() == fragments.end());
+    // When legacy is forced, IsInLayoutNGInlineFormattingContext is false,
+    // and we fall back to normal HasTextBox
+    return FirstTextBox();
+  }
+  return FirstTextBox();
+}
+
 scoped_refptr<StringImpl> LayoutText::OriginalText() const {
   Node* e = GetNode();
   return (e && e->IsTextNode()) ? ToText(e)->DataImpl() : nullptr;
@@ -2298,7 +2311,7 @@ LayoutRect LayoutText::DebugRect() const {
       LayoutRect(IntRect(first_run_offset.X(), first_run_offset.Y(),
                          lines_box.Width(), lines_box.Height()));
   LayoutBlock* block = ContainingBlock();
-  if (block && HasTextBoxes())
+  if (block && HasLegacyTextBoxes())
     block->AdjustChildDebugRect(rect);
 
   return rect;

third_party/WebKit/Source/core/layout/LayoutText.h

@@ -204,7 +204,11 @@ class CORE_EXPORT LayoutText : public LayoutObject {
 
   // True if we have inline text box children which implies rendered text (or
   // whitespace) output.
-  bool HasTextBoxes() const { return FirstTextBox(); }
+  bool HasTextBoxes() const;
+
+  // TODO(layoutng) Legacy-only implementation of HasTextBoxes.
+  // All callers should call HasTextBoxes instead, and take NG into account.
+  bool HasLegacyTextBoxes() const { return FirstTextBox(); }
 
   // Returns the Position in DOM that corresponds to the given offset in the
   // |text_| string.