1) Moved basic utility code into base/ directory to make it clear which code
doesn't depend on Flutter-specific knowldge.
2) Move the CommandRunner subclasses into a runner/ directory because these
aren't commands themselves.
Other changes in this patch:
- Make the 'flutter' tool say "Updating flutter tool..." when it calls
pub get, to avoid confusion about what the pub get output is about.
- Make the bash flutter tool call pub get when the revision has
changed. (This was already happening on Windows.)
- Fix a raft of bugs found by the analyzer.
- Fix some style nits in various bits of code that happened to be near
things the analyzer noticed.
- Remove the logic in "flutter test" that would run "pub get", since
upon further reflexion it was determined it didn't work anyway.
We'll probably have to add better diagnostics here and say to run the
updater script.
- Remove the native velocity tracker script, since it was testing code
that has since been removed.
Notes on ignored warnings:
- We ignore warnings in any packages that are not in the Flutter repo or
in the author's current directory.
- We ignore various irrelevant Strong Mode warnings. We still enable
strong mode because even though it's not really relevant to our needs,
it does (more or less accidentally) catch a few things that are
helpful to us.
- We allow CONSTANTS_LIKE_THIS, since we get some of those from other
platforms that we are copying for sanity and consistency.
- We allow one-member abstract classes since we have a number of them
where it's perfectly reasonable.
- We unfortunately still ignore warnings in mojom.dart autogenerated
files. We should really fix those but that's a separate patch.
- We verify the actual source file when we see the 'Name non-constant
identifiers using lowerCamelCase.' lint, to allow one-letter variables
that use capital letters (e.g. for physics expressions) and to allow
multiple-underscore variable names.
- We ignore all errors on lines that contain the following magic
incantation and a "#" character:
// analyzer doesn't like constructor tear-offs
- For all remaining errors, if the line contains a comment of the form
// analyzer says "..."
...then we ignore any errors that have that "..." string in them.
