* Improve update checking
This change emables pinging the server to check for updates regardless of whether the local version is "out of date". The server code already has a 7-day cache so the result is that we can now ping the server once every 7 days instead of waiting for the local install to be 4 weeks out of date before pinging.
The original 4 week period is still used for when we'll start warning the user they're out of date if we could not confirm with the server whether there's a new version.
* Improve message when we know there's a new version available
* Fix bnullable bool checks
* Switch nullable bool to enum
* Fix casing of enum values
* Remove stale comment
The names are now descriptive so doesn't need additional explanation.
* Improve name of function
* Remove note:
* Rename kPauseToLetUserReadTheMessage -> timeToPauseToLetUserReadTheMessage
* Change kVersionAgeConsideredUpToDate to 5 weeks from 4
* Inline the isNewerFrameworkVersionAvailable check
* Fix indenting (?)
* Fix more indenting
* Rename function to be clearer it's getting the commit date
* Formating tweaks
* Update stamp when connection failed, and reduce time before we'll try again
Previously we would hit the server on every command if we thought we might be out of date and we never successfully connected (eg. if you're offline). This makes the stamp update even when there's a conneciton failure so that this won't happen, but reduces the time till we check again from 7 days to 3 days to compensate a little in case it was a one-off.
https://github.com/flutter/flutter/pull/18193#issuecomment-399222269
* Fix comment
* Don't perform update checks if not on an official channel
* Use already downloaded dart sdk for frontend_server.
This is follow-up to https://github.com/flutter/flutter/pull/14610
* Remove reference to engine dart-sdk from artifacts
* Remove unused imports
* WIP to switch back to solution where dart sdk is downloaded into bin/cache/dart-sdk, but it is 'flutter precache -a' that can download all dart sdks for other platforms under bin/cache/artifacts/engine/<platform>/dart-sdk
* Download all dart sdks when 'flutter precache -a'
Mainly, this adds documentation to members that were previously
lacking documentation.
It also adds a big block of documentation about improving performance
of widgets.
This also removes some references to package:collection and adds
global setEquals and listEquals methods in foundation that we can use.
(setEquals in particular should be much faster than the
package:collection equivalent, though both should be faster as they
avoid allocating new objects.) All remaining references now qualify
the import so we know what our remaining dependencies are.
Also lots of code reordering in Flutter driver to make the code
consistent and apply the style guide more thoroughly.
