#4672

Anywhere that accepted IconData now accepts either an Icon or an
ImageIcon.

Places that used to take an IconData in an `icon` argument, notably
IconButton and DrawerItem, now take a Widget in that slot. You can wrap
the value that used to be passed in in an Icon constructor to get the
same result.

Icon itself now takes the icon as a positional argument, for brevity.

ThemeData now has an iconTheme as well as a primaryIconTheme, the same
way it has had a textTheme and primaryTextTheme for a while.

IconTheme.of() always returns a value now (though that value itself may
have nulls in it). It defaults to the ThemeData.iconTheme.

IconThemeData.fallback() is a new method that returns an icon theme data
structure with all fields filled in.

IconTheme.merge() is a new constructor that takes a context and creates
a widget that mixes in the new values with the inherited values.

Most places that introduced an IconTheme widget now use IconTheme.merge.

IconThemeData.merge and IconThemeData.copyWith act in a way analogous to
the similarly-named members of TextStyle.

ImageIcon is introduced. It acts like Icon but takes an ImageProvider
instead of an IconData.

Also: Fix the analyzer to actually check the stocks app.

This prevents multiple simultaneous runs of the analyzer from stomping
over each other (e.g. multiple runs of 'update-packages'). Certain
long-lived commands (like analyze, run, logs) are exempted once they've
done enough work to be safe from most stomping action.

This still doesn't make us entirely safe from craziness, e.g. if you're
half way through an 'update-packages' run and you call 'git pull', who
knows what state you'll end up in. But there's only so much one can do.

Fixes https://github.com/flutter/flutter/issues/2762

Also, make it clear the screen between results so it's more obvious
what's going on when you have new results (especially when you have
fixed everything).

Disables current package and current directory analysis when files are specified.

Fixes: https://github.com/flutter/flutter/issues/4091.

* working on making a faster flutter run restart

* clean up todos; fire events on isolate changes

* use the Flutter.FrameworkInitialization event

* review comments

* rename service_protocol.dart to protocol_discovery.dart

* add a wrapper around the obs. protocol

* use json-rpc in run

* consolidate obs. code; implement flutter run --benchmark

* review comments

Artifacts from local engine builds will be found based on the --local-engine flag

Updates the analyze command to pass a package map to analysis rather than a file path.

This allows us to avoid creating a needless temporary `.packages` file and host directory and saves us a trip to disk to retrieve the contents when building our URI resolvers for analysis.

Introduces a new Dart analysis wrapper that works directly with the analyzer API (in favor of shelling out to a separate process).

Some consequences:

  * we no longer need to fear parts (simplifying our dart file gathering)
  * we can filter by error code (when needed), rather than by error strings
  * no more IO scraping
  * no need to generate `main()` or to run with `--package-warnings`
  * we now specify an analyzer (and linter) version in the pubspec (we’ll want to make sure this doesn’t diverge too far from the analyzer shipped with the SDK but it does give us some room to play with experimental builds)
  * no more (re)scanning of error source files (and so no more source cache)
  * should generally be a bit simpler and easier to maintain
  * runs a bit faster :)

* simplify the analysis benchmarking code

* review comments

* add a benchmarking mode to flutter analyze

* change arg names

Handy for testing against specific local SDK builds.

(Note that the option is hidden.)

* find all repo packages

* .dartignore

With the new dev build we've got the updated linter and so can use the `@optionalTypeArgs` annotation (in `meta 0.12.0`).

Bonus: this lets us clean up one more Regexp in the `analyze` command! :)

* run pub for analyze and test

* don't run pub when doing repo analysis

* move logic for when to run pub into the commands

* re-write ternary expression

As per https://github.com/dart-lang/sdk/issues/25723, moves last command-line flag to `.analysis_options`.

The push to dev-4 allows us to cleanup a few more bits:
  * `api_docs` lint message special casing (lint fixed)
  * `allowedIdentifiersPattern` (lint fixed)

* better messaging about windows support

* fix lints

* Enable the lint require documentation.

* Track how many public Flutter members lack docs

* Rename the .analysis_options file

This makes Atom happier in the flutter_tools package.

We can work around these in code rather than by post-processing the analyzer
output.