Previously, we lost sync with the tab view contents when switching tabs. Now we
key the subtrees to make sure they keep their state across tab animations.

Fixes #3147

Overscroll indicator for MaterialList

See https://www.google.com/design/spec/style/writing.html#

Also, port the MixedViewport tests to LazyBlockViewport. Fix bugs found by the tests.

* add the dart vm version to flutter doctor

* drop the dart vm change

Fix some legit uses of GlobalKey to specify the type they want.



Fix some sketchy uses of GlobalKey in tests to fake it with "as

dynamic".



Remove some extraneous imports that made the build red.

Previously, the client of PopupMenuButton needed to build all the menu times

when building the PopupMenuButton. This can get expensive if, for example, each
item in a scrollable list has a popup menu associated with it.

Now the client passes a builder function to the PopupMenuButton that gets
invoked only when its time to show the menu items.

Fixes #2855

This patch adds dartdoc to LazyBlock. Also, this patch fixes the scrolling
physics of LazyBlock. Previously, we updated a running simulation only when the
change in scroll behavior changed the current scroll offset. Now we update
running simulations every time the behavior changes because the simulation
might depend on quantities other than the current scroll offset.

Add a `--no-codesign` option to `ios build` to disable code signing.

LazyBlock is going to replace ScrollableMixedWidgetList at some point.

Fix typo in Tooltip's shouldRelayout method.

LazyBlock is intended as a replacement for MixedViewport. Rather than

maintaining a table of all the observed child sizes (like

MixedViewport), LazyBlock works by dead reckoning the location of the

children based on the existing viewport. This approach makes it easier

to resize children because LazyBlock doesn't cache any additional

information that would need to be invalidated.



This patch contains a first draft of LazyBlock that works in a simple

usage scenario. Subsequent patches will replace

ScrollableMixedWidgetList with LazyBlock and port the existing

ScrollableMixedWidgetList tests over to LazyBlock.



Related to #3075

- Rename unselectedColor to unselectedWidgetColor.

- Rename selectionColor to textSelectionColor.

- Add selectedRowColor.

- Remove hintOpacity since it's not tested and has no demo clients.

- Add some docs.

* add a dev/dartdoc.dart script to generate docs for the packages/ packages

* remove description

* rename readme

* change to using --include-external

* move docs to dev/docs

Remove public accessor for paint dirty state

If we use null for these values, the implementations will later assert.



Fixes #3102

This picks up a change which causes ChildViews to jank instead of flicker during resize.

Fixes https://github.com/flutter/flutter/issues/2713

This will let us draw in-row bottom borders and row-wide backgrounds,

both of which are necessary for Material data tables.

Using .of() to call mutating setters is not great practice since it ties

parts of the app together in ways that prevent reuse and composition.



Since people are now using the gallery app to copy from, let's use the

better practice of using callbacks.

Gallery Tweaks

Specifically, explain how to create both determinate and indeterminate progress

indicators.



Fixes #3055

* Enable the lint require documentation.

* Track how many public Flutter members lack docs

* Rename the .analysis_options file

This makes Atom happier in the flutter_tools package.

Fixes #1541

- Create a FlutterErrorDetails struct-like class that describes an

  exception along with more details that aren't in the exception, like

  where it was caught and what was going on when it was caught.



- Provide a FlutterError static API for handling these objects:



  - FlutterError.onError which is called whenever Flutter catches an

    error.



  - FlutterError.reportError() which handles an error.



  - FlutterError.dumpErrorToConsole() which is the default behavior

    for onError.



- Removes all the existing exception handler callbacks.



- Replaces all the existing places that described exceptions using

  debugPrint with calls to FlutterError.reportError().



- Extend lockState() to also catch exceptions, so that we catch

  exceptions that happen during finalizers.



- Make the test framework catch errors and treat them as failures.



- Provide a mechanism to override this behavior in the test framework.



- Make the tests that used to depend on the exception handler

  callbacks use this new mechanism.



- Make pump() also support the phase argument.



- Improve some tests using these new features.



Fixes #2356, #2988, #2985, #2220.

For example, to implement backdrop blur effects.