To make it cleaner when we RTLify these.

* Refactor CupertinoScaffold

* Rename rootTabPageBuilder to tabBuilder

* fix tab transparency padding

* add a CupertinoTab

* Add default background color

* Add a bunch of examples

* A bunch of tests

* Refactor CupertinoScaffold

* Rename rootTabPageBuilder to tabBuilder

* fix tab transparency padding

* Add default background color

* review notes

* fix test

* review

* Rename CupertinoTab to CupertinoTabView

* remove final ; in sample code for analyzer

* Refactor CupertinoScaffold

* Rename rootTabPageBuilder to tabBuilder

* fix tab transparency padding

* Add default background color

* review notes

* fix test

* round 3

* partially address comments

* merge

* review notes

* review

* review

* review

* round 2

* deal with null futures

* review

* review

* review

* review

I inflated instead of deflating. Oops.

Correctly handle the case where the TextEditingController associated
with a TextField is set to null. Due to a typo (= vs ==), previously
this was a no-op and the existing TextEditingController was retained,
rather than copied.

* Add IconThemeData adjustment to ListTile trailing element (makes consistent with leading element)

* Add test for ListTile theme changes

* Pull out and share IconThemeData variable between leading and trailing

* remove extra comma

* fix style nit

Add an RTL version of BorderRadius.
Minor fixes to EdgeInsets to match.

* Record original pointer event timestamp

* review

* review

* review

* Matched motions with iOS. Didn’t add overscroll spring clamps and fix tests yet.

* clamp max overscroll transfer

* Add test

* review notes, moved things around

* remove function passing indirection

* review

* Replace stopwatch with timestamp from #11988

* move static

* Review

* Record original pointer event timestamp

* review

* review

* review

Fixes some tests that weren't aggressively catching exceptions.
Fixes some actual failures that were found because of this.
Tries to fix an intermittent failure with crash1_test.dart which could be a race condition.

Includes:
* DEPS: Change the URL for Dart to the new Gerrit instance. (https://github.com/flutter/engine/pull/4111)
* Add operators to Radius (https://github.com/flutter/engine/pull/4117)

Fix dropdown buttons menus being clipped by the edge of the screen

* upper case

* fix Russian material translations

* regenerate localizations.dart

This will enable both to be RTL'ed.

Also, factor out common border painting code into paintBorder.
Also, make Border paint uniform non-rounded borders using drawRect.
Also, add some documentation about an issue that wasted an hour of my life.
Also, factor out all the border painting code into TableBorder.paint.

* Allow FloatingActionButton to not have a heroTag.
* Allow FloatingActionButton to not have a child.
* Allow Tooltip to not have a child.
* Improve the debug output of the default FloatingActionButton hero tag.
* Improve the error message in the Hero clashing-tag case.
* Improve the debug output of the Hero widget.
* Improve the debug output of gesture-related widgets.
* Minor improvements to documentation.
* Fix some typos in comments.
* Fix some style nits.

Using anchor links from https://github.com/flutter/website/pull/676

* Allow apps to change the title margin in app bar.

* Fix documentation links and the shouldLayout function in the _ToolbarLayout

* Rename margin to spacing

* review comments

* Test fixes. Now we also test the width to make sure enough space is left for trailing widget

* Expose the middle spacing default and use it in app bar.

* Fix analyzer break

* Doc fixes due to review