[LayoutNG] Initial support for the 'vertical-align' property

third_party/WebKit/Source/core/layout/ng/inline/ng_line_height_metrics.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/ng/inline/ng_line_height_metrics.h"
 
 #include "core/style/ComputedStyle.h"
 
 namespace blink {
 
 NGLineHeightMetrics::NGLineHeightMetrics(const ComputedStyle& style,
                                          FontBaseline baseline_type) {
   const SimpleFontData* font_data = style.GetFont().PrimaryFont();
   DCHECK(font_data);
   Initialize(font_data->GetFontMetrics(), baseline_type);
 }
 
 NGLineHeightMetrics::NGLineHeightMetrics(const FontMetrics& font_metrics,
                                          FontBaseline baseline_type) {
   Initialize(font_metrics, baseline_type);
 }
 
 void NGLineHeightMetrics::Initialize(const FontMetrics& font_metrics,
                                      FontBaseline baseline_type) {
   ascent = font_metrics.FixedAscent(baseline_type);
   descent = font_metrics.FixedDescent(baseline_type);
 }
 
 void NGLineHeightMetrics::AddLeading(LayoutUnit line_height) {
+  DCHECK(!IsEmpty());
   LayoutUnit half_leading = (line_height - (ascent + descent)) / 2;
   // TODO(kojii): floor() is to make text dump compatible with legacy test
   // results. Revisit when we paint.
   ascent += half_leading.Floor();
   descent = line_height - ascent;
 }
 
+void NGLineHeightMetrics::Move(LayoutUnit delta) {
+  DCHECK(!IsEmpty());
+  ascent -= delta;
+  descent += delta;
+}
+
 void NGLineHeightMetrics::Unite(const NGLineHeightMetrics& other) {
   ascent = std::max(ascent, other.ascent);
   descent = std::max(descent, other.descent);
 }
 
 }  // namespace blink