The app header would sometimes mistakenly not get rendered while on the
Home screen. This could happen when a permission request was made while
the UI was open, to either the browser action popup or the fullscreen
UI.
This was caused by faulty logic in the top-level router component. It
would hide the app header if there was a pending permission request,
presumably because the author assumed that a redirect to the permission
flow would shortly follow. This redirect only happens on mount though,
not if the UI was already open when the permission request was
submitted.
The intent of this logic was to hide a brief flash of the app header
prior to rendering the permission flow. This brief flash has now been
restored, which is unfortunate, but is better than the missing app
header bug. We can revisit a solution to removing this flash in the
future, hopefully in a manner that avoids this bug and works for all
notification UI cases.
A new page has been created for viewing assets. This replaces the old
`selectedToken` state, which previously would augment the home page
to show token-specific information.
The new asset page shows the standard token overview as seen previously
on the home page, plus a history filtered to show just transactions
relevant to that token.
The actions that were available in the old token list menu have been
moved to a "Token Options" menu that mirrors the "Account Options"
menu.
The `selectedTokenAddress` state has been removed, as it is no longer
being used for anything.
`getMetaMetricState` has been renamed to `getBackgroundMetaMetricState`
because its sole purpose is extracting data from the background state
to send metrics from the background. It's not really a selector, but
it was convenient for it to use the same selectors the UI uses to
extract background data, so I left it there for now.
A new Redux store has been added to track state related to browser history.
The most recent "overview" page (i.e. the home page or the asset page) is
currently being tracked, so that actions taken from the asset page can return
the user back to the asset page when the action has finished.
