Support animating <angle> custom properties

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

Index: third_party/WebKit/Source/core/animation/CSSAngleInterpolationType.cpp
diff --git a/third_party/WebKit/Source/core/animation/CSSAngleInterpolationType.cpp b/third_party/WebKit/Source/core/animation/CSSAngleInterpolationType.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..c8f9a949b7b0bb5b95939a43d7a325229b56e791
--- /dev/null
+++ b/third_party/WebKit/Source/core/animation/CSSAngleInterpolationType.cpp
@@ -0,0 +1,35 @@
+// 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/animation/CSSAngleInterpolationType.h"
+
+#include "core/css/CSSPrimitiveValue.h"
+
+namespace blink {
+
+InterpolationValue CSSAngleInterpolationType::maybeConvertNeutral(
+    const InterpolationValue&,
+    ConversionCheckers&) const {
+  return InterpolationValue(InterpolableNumber::create(0));
+}
+
+InterpolationValue CSSAngleInterpolationType::maybeConvertValue(
+    const CSSValue& value,
+    const StyleResolverState*,
+    ConversionCheckers&) const {
+  if (!value.isPrimitiveValue() || !toCSSPrimitiveValue(value).isAngle())
+    return nullptr;
+  return InterpolationValue(
+      InterpolableNumber::create(toCSSPrimitiveValue(value).computeDegrees()));
+}
+
+const CSSValue* CSSAngleInterpolationType::createCSSValue(
+    const InterpolableValue& value,
+    const NonInterpolableValue*,
+    const StyleResolverState&) const {
+  return CSSPrimitiveValue::create(toInterpolableNumber(value).value(),
+                                   CSSPrimitiveValue::UnitType::Degrees);
+}
+
+}  // namespace blink