Support animating <angle> custom properties

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

Index: third_party/WebKit/Source/core/animation/CSSAngleInterpolationType.h
diff --git a/third_party/WebKit/Source/core/animation/CSSAngleInterpolationType.h b/third_party/WebKit/Source/core/animation/CSSAngleInterpolationType.h
new file mode 100644
index 0000000000000000000000000000000000000000..54558284ec5557ca959464be099b7bf41f82b910
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+++ b/third_party/WebKit/Source/core/animation/CSSAngleInterpolationType.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 CSSAngleInterpolationType_h
+#define CSSAngleInterpolationType_h
+
+#include "core/animation/CSSInterpolationType.h"
+
+namespace blink {
+
+class CSSAngleInterpolationType : public CSSInterpolationType {
+ public:
+  CSSAngleInterpolationType(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.
+  // CSSAngleInterpolationType 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  // CSSAngleInterpolationType_h