[NGFragmentItem] Add NGFragmentItem::Style()

This patch adds |NGFragmentItem::Style()|, by sharing the
code between |NGPhysicalFragment|.

Bug: 982194
Change-Id: I7153fb18df7aaa3e7d04995e1d99553fbf637d85
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1768604
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690384}

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

@@ -1844,6 +1844,26 @@ bool LayoutObject::IsSelectable() const {
                          StyleRef().UserModify() == EUserModify::kReadOnly);
 }
 
+const ComputedStyle& LayoutObject::SlowEffectiveStyle(
+    NGStyleVariant style_variant) const {
+  switch (style_variant) {
+    case NGStyleVariant::kStandard:
+      return StyleRef();
+    case NGStyleVariant::kFirstLine:
+      return FirstLineStyleRef();
+    case NGStyleVariant::kEllipsis:
+      // The ellipsis is styled according to the line style.
+      // https://www.w3.org/TR/css-overflow-3/#ellipsing-details
+      // Use first-line style if exists since most cases it is the first line.
+      DCHECK(IsInline());
+      if (LayoutObject* block = ContainingBlock())
+        return block->FirstLineStyleRef();
+      return FirstLineStyleRef();
+  }
+  NOTREACHED();
+  return StyleRef();
+}
+
 // Called when an object that was floating or positioned becomes a normal flow
 // object again. We have to make sure the layout tree updates as needed to
 // accommodate the new normal flow object.

third_party/blink/renderer/core/layout/layout_object.h

@@ -46,6 +46,7 @@
 #include "third_party/blink/renderer/core/layout/layout_object_child_list.h"
 #include "third_party/blink/renderer/core/layout/map_coordinates_flags.h"
 #include "third_party/blink/renderer/core/layout/ng/ng_outline_type.h"
+#include "third_party/blink/renderer/core/layout/ng/ng_style_variant.h"
 #include "third_party/blink/renderer/core/layout/subtree_layout_scope.h"
 #include "third_party/blink/renderer/core/loader/resource/image_resource_observer.h"
 #include "third_party/blink/renderer/core/paint/compositing/compositing_state.h"
@@ -1770,6 +1771,12 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
   inline const ComputedStyle* Style(bool first_line) const;
   inline const ComputedStyle& StyleRef(bool first_line) const;
 
+  const ComputedStyle& EffectiveStyle(NGStyleVariant style_variant) const {
+    return style_variant == NGStyleVariant::kStandard
+               ? StyleRef()
+               : SlowEffectiveStyle(style_variant);
+  }
+
   static inline Color ResolveColor(const ComputedStyle& style_to_use,
                                    const CSSProperty& color_property) {
     return style_to_use.VisitedDependentColor(color_property);
@@ -2554,6 +2561,8 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
   };
   virtual bool IsOfType(LayoutObjectType type) const { return false; }
 
+  const ComputedStyle& SlowEffectiveStyle(NGStyleVariant style_variant) const;
+
   // Updates only the local style ptr of the object.  Does not update the state
   // of the object, and so only should be called when the style is known not to
   // have changed (or from SetStyle).

third_party/blink/renderer/core/layout/ng/inline/ng_fragment_item.h

@@ -7,6 +7,7 @@
 
 #include "third_party/blink/renderer/core/core_export.h"
 #include "third_party/blink/renderer/core/layout/geometry/logical_offset.h"
+#include "third_party/blink/renderer/core/layout/layout_object.h"
 #include "third_party/blink/renderer/core/layout/ng/inline/ng_line_box_fragment_builder.h"
 #include "third_party/blink/renderer/core/layout/ng/inline/ng_line_height_metrics.h"
 #include "third_party/blink/renderer/platform/graphics/paint/display_item_client.h"
@@ -72,8 +73,14 @@ class CORE_EXPORT NGFragmentItem : public DisplayItemClient {
   bool UsesFirstLineStyle() const {
     return StyleVariant() == NGStyleVariant::kFirstLine;
   }
+  // Returns the style for this fragment.
+  //
+  // For a line box, this returns the style of the containing block. This mostly
+  // represents the style for the line box, except 1) |style.Direction()| maybe
+  // incorrect, use |BaseDirection()| instead, and 2) margin/border/padding,
+  // background etc. do not apply to the line box.
   const ComputedStyle& Style() const {
-    return layout_object_->StyleRef(UsesFirstLineStyle());
+    return layout_object_->EffectiveStyle(StyleVariant());
   }
   const LayoutObject* GetLayoutObject() const { return layout_object_; }
 

third_party/blink/renderer/core/layout/ng/ng_physical_fragment.cc

@@ -269,28 +269,6 @@ void NGPhysicalFragment::Destroy() const {
   }
 }
 
-const ComputedStyle& NGPhysicalFragment::SlowEffectiveStyle() const {
-  switch (StyleVariant()) {
-    case NGStyleVariant::kStandard:
-      return layout_object_.StyleRef();
-    case NGStyleVariant::kFirstLine:
-      return layout_object_.FirstLineStyleRef();
-    case NGStyleVariant::kEllipsis:
-      DCHECK_EQ(Type(), kFragmentText);
-      DCHECK_EQ(StyleVariant(), NGStyleVariant::kEllipsis);
-      // The ellipsis is styled according to the line style.
-      // https://drafts.csswg.org/css-ui/#ellipsing-details
-      // Use first-line style if exists since most cases it is the first line.
-      // TODO(kojii): Should determine if it's really in the first line.
-      DCHECK(layout_object_.IsInline());
-      if (LayoutObject* block = layout_object_.ContainingBlock())
-        return block->FirstLineStyleRef();
-      return layout_object_.FirstLineStyleRef();
-  }
-  NOTREACHED();
-  return layout_object_.StyleRef();
-}
-
 Node* NGPhysicalFragment::GetNode() const {
   return !IsLineBox() ? layout_object_.GetNode() : nullptr;
 }

third_party/blink/renderer/core/layout/ng/ng_physical_fragment.h

@@ -171,9 +171,7 @@ class CORE_EXPORT NGPhysicalFragment
   // incorrect, use |BaseDirection()| instead, and 2) margin/border/padding,
   // background etc. do not apply to the line box.
   const ComputedStyle& Style() const {
-    return StyleVariant() == NGStyleVariant::kStandard
-               ? layout_object_.StyleRef()
-               : SlowEffectiveStyle();
+    return layout_object_.EffectiveStyle(StyleVariant());
   }
   Node* GetNode() const;