Stop checking InlineTextBox in HasRenderedNonAnonymousDescendantsWith…

…Height

HasRenderedNonAnonymousDescendantsWithHeight is a subroutine called
during position canonicalization to detect caret positions in empty
blocks. Its current dependency on legacy inline structure blocks the
NG conversion of canonicalization.

This patch changes the above mentioned function to decouple it from
legacy InlineTextBox, to make editing work better with LayoutNG.

Although the function still relies on InlineBox after the patch
(via LayoutInline::LinesBoundingBox), at least we get an NG version of
canonicalization that works in most cases, i.e., when there are text
nodes. In other words, this patch allows us to run canonicalization in
the NG world in most cases.

Note: there is no need to enable layout_ng bot in this patch because
the bot doesn't have LayoutNGPaintFragments enabled, and hence, the patch
has no effect there.

Bug: 771398
Change-Id: Idbd595b0a2776dd843840a1ab903f5de7d9d5d59
Reviewed-on: https://chromium-review.googlesource.com/729040
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510387}

third_party/WebKit/Source/core/editing/VisibleUnits.cpp

@@ -770,13 +770,15 @@ static LayoutUnit BoundingBoxLogicalHeight(LayoutObject* o,
 // TODO(crbug.com/766448): Change parameter type to |const LayoutObject*|.
 bool HasRenderedNonAnonymousDescendantsWithHeight(LayoutObject* layout_object) {
   LayoutObject* stop = layout_object->NextInPreOrderAfterChildren();
+  // TODO(editing-dev): Avoid single-character parameter names.
   for (LayoutObject* o = layout_object->SlowFirstChild(); o && o != stop;
        o = o->NextInPreOrder()) {
     if (o->NonPseudoNode()) {
-      if ((o->IsText() &&
-           BoundingBoxLogicalHeight(o, ToLayoutText(o)->LinesBoundingBox())) ||
+      if ((o->IsText() && ToLayoutText(o)->HasNonCollapsedText()) ||
           (o->IsBox() && ToLayoutBox(o)->PixelSnappedLogicalHeight()) ||
           (o->IsLayoutInline() && IsEmptyInline(LineLayoutItem(o)) &&
+           // TODO(crbug.com/771398): Find alternative ways to check whether an
+           // empty LayoutInline is rendered, without checking InlineBox.
            BoundingBoxLogicalHeight(o, ToLayoutInline(o)->LinesBoundingBox())))
         return true;
     }