Don't assume line-height properties can't change between text and its container.

third_party/WebKit/Source/core/layout/line/InlineFlowBox.cpp

 /*
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc.
  *               All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 73 matching lines @@
     const ComputedStyle& parent_style,
     const ComputedStyle& child_style,
     bool is_root) {
   return parent_style.HasIdenticalAscentDescentAndLineGap(child_style) &&
          parent_style.LineHeight() == child_style.LineHeight() &&
          (parent_style.VerticalAlign() == EVerticalAlign::kBaseline ||
           is_root) &&
          child_style.VerticalAlign() == EVerticalAlign::kBaseline;
 }
 
+static inline bool ParentIsDOMParent(LineLayoutItem parent,
+                                     LineLayoutItem child) {
+  return child.GetNode() &&
+         FlatTreeTraversal::Parent(*child.GetNode()) == parent.GetNode();

[eae, 2017/04/21 10:54:52]

Can child.GetNode() ever be null? Might be worth adding a DCHECK here.

+}
+
 void InlineFlowBox::AddToLine(InlineBox* child) {
   DCHECK(!child->Parent());
   DCHECK(!child->NextOnLine());
   DCHECK(!child->PrevOnLine());
   CheckConsistency();
 
   child->SetParent(this);
   if (!first_child_) {
     first_child_ = child;
     last_child_ = child;
@@ skipping 18 matching lines @@
     const ComputedStyle& parent_style =
         GetLineLayoutItem().StyleRef(IsFirstLineStyle());
     const ComputedStyle& child_style =
         child->GetLineLayoutItem().StyleRef(IsFirstLineStyle());
     bool root = IsRootInlineBox();
     bool should_clear_descendants_have_same_line_height_and_baseline = false;
     if (child->GetLineLayoutItem().IsAtomicInlineLevel()) {
       should_clear_descendants_have_same_line_height_and_baseline = true;
     } else if (child->IsText()) {
       if (child->GetLineLayoutItem().IsBR() ||
-          (child->GetLineLayoutItem().Parent() != GetLineLayoutItem())) {
+          child->GetLineLayoutItem().Parent() != GetLineLayoutItem() ||
+          !ParentIsDOMParent(GetLineLayoutItem(), child->GetLineLayoutItem())) {
         if (!HasIdenticalLineHeightProperties(parent_style, child_style, root))
           should_clear_descendants_have_same_line_height_and_baseline = true;
       }
       if (child_style.HasTextCombine() ||
           child_style.GetTextEmphasisMark() != kTextEmphasisMarkNone)
         should_clear_descendants_have_same_line_height_and_baseline = true;
     } else {
       if (child->GetLineLayoutItem().IsBR()) {
         // FIXME: This is dumb. We only turn off because current layout test
         // results expect the <br> to be 0-height on the baseline.
@@ skipping 1610 matching lines @@
     DCHECK_EQ(child->prevOnLine(), prev);
     prev = child;
   }
   DCHECK_EQ(prev, m_lastChild);
 #endif
 }
 
 #endif
 
 }  // namespace blink