Fewer reused duplicate symbol names in animation.

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

Index: third_party/WebKit/Source/core/animation/SideIndex.h
diff --git a/third_party/WebKit/Source/core/animation/SideIndex.h b/third_party/WebKit/Source/core/animation/SideIndex.h
new file mode 100644
index 0000000000000000000000000000000000000000..8ac725cf918c2a99103bcd511979e77323c19104
--- /dev/null
+++ b/third_party/WebKit/Source/core/animation/SideIndex.h
@@ -0,0 +1,20 @@
+// 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 SideIndex_h
+#define SideIndex_h
+
+namespace blink {
+
+enum SideIndex : unsigned {
+  SideTop,
+  SideRight,
+  SideBottom,
+  SideLeft,
+  SideIndexCount,
+};
+
+}  // namespace blink
+
+#endif  // SideIndex_h