Sort page actions before comparing them to the list of page action views
This fixes an issue where PageActionDiffer would report differences on
every call if the external bookmark manager was installed and the user
had any other extension with a page action and an id preceding that of
the bookmark manager. This would cause the page action UI elements to be
constantly destroyed and rebuilt.
BUG=465595,465449
Review URL: https://codereview.chromium.org/
993063003
Cr-Commit-Position: refs/heads/master@{#320371}