This method controls whether the builder needs to be called again again even if the layout constraints are the same.
By default, the builder will always be called when the widget is updated because the logic in the callback might have changed. However, there are cases where subclasses of ConstrainedLayoutBuilder know that certain property updates only affect paint and not build. In these cases, we lack a way of expressing that the builder callback is not needed -- and we end up doing superfluous work.
This PR gives subclasses the ability to know exactly when the callback needs to be called and when it can be skipped.
Avoid calling `builder` in `ConstrainedLayoutBuilder` when layout constraints are the same.
[Design doc](flutter.dev/go/layout-builder-optimization).
## Related Issues
Fixes https://github.com/flutter/flutter/issues/6469
* 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
* 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
