Refactor LayoutInline::addOutlineRects to avoid tricky logic to avoid dups

Source/core/layout/LayoutBoxModelObject.cpp

Index: Source/core/layout/LayoutBoxModelObject.cpp
diff --git a/Source/core/layout/LayoutBoxModelObject.cpp b/Source/core/layout/LayoutBoxModelObject.cpp
index 322bb7e4a5ebb6323025e044c5ed1568a0ac6880..1cf99d2bc82979715fcac0c08540c58d41ba5ed1 100644
--- a/Source/core/layout/LayoutBoxModelObject.cpp
+++ b/Source/core/layout/LayoutBoxModelObject.cpp
@@ -414,6 +414,15 @@ void LayoutBoxModelObject::addOutlineRectsForDescendant(const LayoutObject& desc
         return;
     }
 
+    if (descendant.isLayoutInline()) {
+        // As an optimization, an ancestor has added rects for its line boxes covering descendants'
+        // line boxes, so descendants don't need to add line boxes again. For example, if the parent
+        // is a LayoutBlock, it adds rects for its RootOutlineBoxes which cover the line boxes of
+        // this LayoutInline. So the LayoutInline needs to add rects for children and continuations only.
+        toLayoutInline(descendant).addOutlineRectsForChildrenAndContinuations(rects, additionalOffset);
+        return;
+    }
+
     descendant.addOutlineRects(rects, additionalOffset);
 }