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diff --git a/chromium/third_party/blink/renderer/core/animation/scroll_timeline_offset.h b/chromium/third_party/blink/renderer/core/animation/scroll_timeline_offset.h
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+++ b/chromium/third_party/blink/renderer/core/animation/scroll_timeline_offset.h
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+// Copyright 2020 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 THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_SCROLL_TIMELINE_OFFSET_H_
+#define THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_SCROLL_TIMELINE_OFFSET_H_
+
+#include "third_party/blink/renderer/bindings/core/v8/v8_scroll_timeline_element_based_offset.h"
+#include "third_party/blink/renderer/core/css/properties/css_parsing_utils.h"
+#include "third_party/blink/renderer/core/scroll/scroll_types.h"
+
+namespace blink {
+
+class StringOrScrollTimelineElementBasedOffset;
+
+// Represent a scroll timeline start/end offset which can be an
+// scroll offset or an element based offset
+class CORE_EXPORT ScrollTimelineOffset final
+    : public GarbageCollected<ScrollTimelineOffset> {
+ public:
+  static ScrollTimelineOffset* Create(
+      const StringOrScrollTimelineElementBasedOffset& offset,
+      const CSSParserContext& context);
+
+  // Create a default offset representing 'auto'.
+  ScrollTimelineOffset() = default;
+  // Create a scroll based offset.
+  explicit ScrollTimelineOffset(CSSPrimitiveValue*);
+  // Create an element based offset.
+  explicit ScrollTimelineOffset(ScrollTimelineElementBasedOffset*);
+
+  void Trace(blink::Visitor*);
+
+  // Resolves this offset against the scroll source and in the given orientation
+  // returning eqiuvalent concrete scroll offset.
+  //
+  //  - Length-based values are converted into concrete length values resolving
+  //    percentages and zoom factor.
+  //  - Element-based values are resolved to the equivalent scroll offset that
+  //    satisfy the requirement.
+  //  - Auto value simply returns the |detfault_offset|.
+  //
+  // max offset is expected to be the maximum scroll offset in the scroll
+  // orientation.
+  double ResolveOffset(Node* scroll_source,
+                       ScrollOrientation,
+                       double max_offset,
+                       double default_offset);
+
+  StringOrScrollTimelineElementBasedOffset
+  ToStringOrScrollTimelineElementBasedOffset() const;
+
+ private:
+  // We either have an scroll or element based offset so at any time one of
+  // these is null. If both are null, it represents the default value of
+  // 'auto'.
+  Member<CSSPrimitiveValue> length_based_offset_;
+  Member<ScrollTimelineElementBasedOffset> element_based_offset_;
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_SCROLL_TIMELINE_OFFSET_H_