[LayoutNG] Compute baseline from fragment tree

third_party/WebKit/Source/core/layout/ng/inline/ng_baseline.h

Index: third_party/WebKit/Source/core/layout/ng/inline/ng_baseline.h
diff --git a/third_party/WebKit/Source/core/layout/ng/inline/ng_baseline.h b/third_party/WebKit/Source/core/layout/ng/inline/ng_baseline.h
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+// 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.
+
+#ifndef NGBaseline_h
+#define NGBaseline_h
+
+#include "platform/LayoutUnit.h"
+#include "platform/fonts/FontBaseline.h"
+
+namespace blink {
+
+class LayoutBox;
+class NGLayoutInputNode;
+
+enum class NGBaselineAlgorithmType {
+  // Compute baselines for atomic inlines.
+  kAtomicInline,
+  // Compute baselines for atomic inlines using the first line style.
+  kAtomicInlineForFirstLine,
+  // Compute baseline of first line box.
+  kFirstLine
+};
+
+// Baselines are products of layout.
+// To compute baseline, add requests to NGConstraintSpace and run Layout().
+struct NGBaselineRequest {
+  NGBaselineAlgorithmType algorithm_type;
+  FontBaseline baseline_type;
+};
+
+// Represents a computed baseline position.
+struct NGBaseline {
+  NGBaselineAlgorithmType algorithm_type;
+  FontBaseline baseline_type;
+  LayoutUnit offset;
+
+  // @return if the node needs to propagate baseline requests/results.
+  static bool ShouldPropagateBaselines(const NGLayoutInputNode);
+  static bool ShouldPropagateBaselines(LayoutBox*);
+};
+
+}  // namespace blink
+
+#endif  // NGBaseline_h