The gr-change-actions element organizes change actions into a single,
sorted array property for rendering. Formerly, the order was partially
established by keeping the actions in separate arrays and rendering
them in serial loops, whereas, with this change, the rendering and order
is simplified and less redundant.
In particular, the `_computeChangeActionValues` and
`_computeRevisionActionValues` methods are merged into a new
`_computeAllActions` method.
Change-Id: I4ff3d1458fe845e0a5932e4aeb6b91dcbb4c20ee
a9807e4c74