Support animating <time> custom properties

third_party/WebKit/Source/core/animation/CSSTimeInterpolationType.h

Index: third_party/WebKit/Source/core/animation/CSSTimeInterpolationType.h
diff --git a/third_party/WebKit/Source/core/animation/CSSTimeInterpolationType.h b/third_party/WebKit/Source/core/animation/CSSTimeInterpolationType.h
new file mode 100644
index 0000000000000000000000000000000000000000..4f868e77e215a2d91897fc4caaeae5d968e767ee
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+++ b/third_party/WebKit/Source/core/animation/CSSTimeInterpolationType.h
@@ -0,0 +1,58 @@
+// 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 CSSTimeInterpolationType_h
+#define CSSTimeInterpolationType_h
+
+#include "core/animation/CSSInterpolationType.h"
+
+namespace blink {
+
+class CSSTimeInterpolationType : public CSSInterpolationType {
+ public:
+  CSSTimeInterpolationType(PropertyHandle property)
+      : CSSInterpolationType(property) {
+    DCHECK(property.isCSSCustomProperty());
+  }
+
+  InterpolationValue maybeConvertNeutral(const InterpolationValue& underlying,
+                                         ConversionCheckers&) const final;
+  InterpolationValue maybeConvertValue(const CSSValue&,
+                                       const StyleResolverState*,
+                                       ConversionCheckers&) const final;
+
+  const CSSValue* createCSSValue(const InterpolableValue&,
+                                 const NonInterpolableValue*,
+                                 const StyleResolverState&) const final;
+
+ private:
+  // These methods only apply to CSSInterpolationTypes used by standard CSS
+  // properties.
+  // CSSTimeInterpolationType is only accessible via registered custom CSS
+  // properties.
+  InterpolationValue maybeConvertStandardPropertyUnderlyingValue(
+      const ComputedStyle&) const final {
+    NOTREACHED();
+    return nullptr;
+  }
+  void applyStandardPropertyValue(const InterpolableValue&,
+                                  const NonInterpolableValue*,
+                                  StyleResolverState&) const final {
+    NOTREACHED();
+  }
+  InterpolationValue maybeConvertInitial(const StyleResolverState&,
+                                         ConversionCheckers&) const final {
+    NOTREACHED();
+    return nullptr;
+  }
+  InterpolationValue maybeConvertInherit(const StyleResolverState&,
+                                         ConversionCheckers&) const final {
+    NOTREACHED();
+    return nullptr;
+  }
+};
+
+}  // namespace blink
+
+#endif  // CSSTimeInterpolationType_h