Use element id's for animations

third_party/WebKit/Source/platform/graphics/CompositorElementId.h

Index: third_party/WebKit/Source/platform/graphics/CompositorElementId.h
diff --git a/third_party/WebKit/Source/platform/graphics/CompositorElementId.h b/third_party/WebKit/Source/platform/graphics/CompositorElementId.h
new file mode 100644
index 0000000000000000000000000000000000000000..d9fc3478fb64a75fd7c4206b9be2b9a65bfe35d4
--- /dev/null
+++ b/third_party/WebKit/Source/platform/graphics/CompositorElementId.h
@@ -0,0 +1,28 @@
+// Copyright 2016 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 CompositorElementId_h
+#define CompositorElementId_h
+
+#include "cc/animation/element_id.h"
+#include "platform/PlatformExport.h"
+
+namespace blink {
+
+struct PLATFORM_EXPORT CompositorSubElementId {

[jbroman, 2016/06/02 20:20:21]

PLATFORM_EXPORT does nothing here

[Ian Vollick, 2016/06/03 19:31:21]

Removed.

+    enum class Value {

[jbroman, 2016/06/02 20:20:21]

What's the point of an enum class nested inside a struct? This means that a
value must always have two scope resolution operators (::), like
CompositorSubElementId::Value::Primary. It looks like this enum class should
just live in the blink namespace, and the surrounding struct can go away, no?

[Ian Vollick, 2016/06/03 19:31:21]

Yes, this is much better. Done.

+        Primary = 1,
+        Scroll = 2,
+        ViewportScroll = 3,
+        LinkHighlight = 4
+    };
+};
+
+using CompositorElementId = cc::ElementId;
+
+CompositorElementId PLATFORM_EXPORT createCompositorElementId(int domNodeId, CompositorSubElementId::Value);
+
+} // namespace blink
+
+#endif // CompositorElementId_h