Remove obsolete flags.
- Remove command line flags enable-toolbar-swipe-in-document-mode and
enable-tab-switcher-in-document-mode.
- Several corresponding methods in FeatureUtilities have become
obsolete as it is no longer possible to have the tab switcher
enabled in document mode.
BUG=
612245
Committed:
https://crrev.com/989b9ede81502507d5dc5bb8872f6535ce264d23
Cr-Commit-Position: refs/heads/master@{#405177}