* Update project.pbxproj files to say Flutter rather than Chromium

Also, the templates now have an empty organization so that we don't cause people to give their apps a Flutter copyright.

* Update the copyright notice checker to require a standard notice on all files

* Update copyrights on Dart files. (This was a mechanical commit.)

* Fix weird license headers on Dart files that deviate from our conventions; relicense Shrine.

Some were already marked "The Flutter Authors", not clear why. Their
dates have been normalized. Some were missing the blank line after the
license. Some were randomly different in trivial ways for no apparent
reason (e.g. missing the trailing period).

* Clean up the copyrights in non-Dart files. (Manual edits.)

Also, make sure templates don't have copyrights.

* Fix some more ORGANIZATIONNAMEs

No code changes, just comments: I spell-checked all the comments in the repo.

* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

* Improve documentation

* Potential performance win in hit testing

Rather than copying the list every time we access `path`, this just
exposes it as an `Iterable`. People who want to copy it can use
`toList()`.

(This isn't a breaking change since code that expects a `List` is
still going to get one.)

* Enforce the Oxford Comma.

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

It was causing problems rolling Flutter into Fuchsia

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

https://github.com/flutter/flutter/issues/17956

* Add a `debugInstrumentAction()` method that will wrap an action
  in a stopwatch and print the time it took to run the action.
* Add a global `debugInstrumentationEnabled` that will control
  whether `debugInstrumentAction()` does anything (even in debug
  builds).
* Add some basic instrumentation to `registerServiceExtension()`
* Temporarily enable the `debugInstrumentationEnabled` flag in the
  Gallery to give us better visibility into what's happening in
  https://github.com/flutter/flutter/issues/17956

...and fix bugs that the tests uncovered.

WRITE TEST FIND BUG