* 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

This reverts commit baea9bf7.

Additionally,   we let the test run on mac8 with iphonexs because the test won't run on Xcode 10.1 (mac3-7). Hence we force it to run on mac8 which currently has Xcode 10.2.

This reverts commit 67b5bdf9.

Reason: it broke device lab.

TBR: @goderbauer 

This reverts commit f1e7fe81.

This fix is in https://github.com/flutter/packages/pull/39

This reverts commit 652be88e.

This fix is in https://github.com/flutter/packages/pull/37

This reverts commit af9f424d.

Reverts flutter/flutter#39439

Reason: this passed the local device lab test on my Macbook but it failed in the actual device lab. Will investigate, fix, and reland.

TBR: @dnfield @goderbauer @tvolkert @Hixie 

For https://github.com/flutter/flutter/issues/33899

Test added:
- simple_animation_perf_ios

Test modified:
- backdrop_filter_perf_ios__timeline_summary

We'll add the CPU/GPU measurement to more iOS tests
once it's proven to be non-flaky.