Change cc::ElementId to be a uint64_t

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

 // 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.
 
 #include "platform/graphics/CompositorElementId.h"
 
 namespace blink {
 
 CompositorElementId CreateCompositorElementId(
     int dom_node_id,
     CompositorSubElementId sub_element_id) {
-  return CompositorElementId(dom_node_id, static_cast<int>(sub_element_id));
+  DCHECK(dom_node_id > 0 && dom_node_id < std::numeric_limits<int>::max() / 4);

[suzyh_UTC10 (ex-contributor), 2017/05/05 04:27:31]

Please make this 4 a named constant or similar rather than a magic number, to
make it clear why this holds.

[chrishtr, 2017/05/05 05:34:52]

Done.

+  int element_id = dom_node_id;

[suzyh_UTC10 (ex-contributor), 2017/05/05 04:27:31]

Use one of the unsigned types rather than int?

[chrishtr, 2017/05/05 05:34:52]

Done. Sorry for forgetting to update this file.

+  element_id = element_id << 2;  // Shift to make room for enum bits.

[suzyh_UTC10 (ex-contributor), 2017/05/05 04:27:31]

Nit: specify "sub_element_id enum bits"

[chrishtr, 2017/05/05 05:34:52]

Done.

+  element_id += static_cast<int>(sub_element_id);
+  return CompositorElementId(element_id);
+}
+
+int DomNodeIdFromCompositorElementId(CompositorElementId id) {
+  return id >> 2;
 }
 
 }  // namespace blink