Applies media padding (e.g. iPhone X safe area insets) to the Material Design demos in the Gallery.
Covers the following demos:
* Buttons (via the TabbedComponentDemoScaffold change)
* Cards
* Expansion panels
* Grid list
* Icons
* Images (via the TabbedComponentDemoScaffold change)
* Page Selector
* Progress Indicator
* Scrollable tabs
* Selection controls (via the TabbedComponentDemoScaffold change)
* Snack bar
* Tabs
* Text fields
* Tooltips
Fixes#13594
After this patch, there are three major text input widgets:
* EditableText. This widget is a low-level editing control that
interacts with the IME and displays a blinking cursor.
* TextField. This widget is a Material Design text field, with all the
bells and whistles. It is highly configurable and can be reduced down
to a fairly simple control by setting its `decoration` property to
null.
* TextFormField. This widget is a FormField that wraps a TextField.
This patch also replaces the InputValue data model for these widgets
with a Listenable TextEditingController, which is much more flexible.
Fixes#7031
* Add cupertino to gallery and add CupertinoButto
* Use single quotes
* Add disabled state
* Some review notes
* Make button animation more responsive and tweak timing
* Renamed things Cupertino
* Button with background, move cupertino demos, move material demos
* Move 2 level list too
* Refactor various demo route names
* Some review notes
* More reviews and add test
* Linter as
* Move private constant up
