The following were previously marked as deprecated over a month ago:
* `FlutterStandardBigInteger`
* `-[FlutterDartProject initFromDefaultSourceForConfiguration]`

Remove their implementations and mark them as unavailable.

Add a `-[FlutterViewController splashScreenView]` property

Add a `-[FlutterViewController splashScreenView]` property that
clients can use to customize the launch view (issue #17140).

This allows plugins to pass extra parameters from the Dart side to the
platform view constructor.

In Android O removing the ViewTreeObserver.onDrawListener from the
listener call crashes. Instead we post a runnable to remove it.

The default WindowManager implementation in Android's Presentation is
delegating addView/removeView/updateViewLayout calls to the global
WindowManager.
This can result in a crash when an embedded view is trying to e.g show a
PopupWindow.

This change adds a custom WindowManager that overrides
addView (and removeView/updateViewLayout) and adds the view to the
presentation's view tree.

Note that views might keep a reference to the window manager which
might be an issue when we move a view from one virtual display to
another (due to a resize). For this reason when re-sizing we are not
creating a new window manager for the new presentation, but updating the
window manager's references to be relevant for the new presentation and
re-use it.

If `FlutterDartProject` found an `FLTLibraryPath` entry in an iOS
application's `Info.plist`, it assumed that values that were valid
filesystem paths were paths to bundles.  If the attempt to retrieve
the `NSBundle` fails, `FlutterDartProject` ignored the failure and
then would assign `nil` to a C++ `std::string`, resulting in a null
pointer dereference.

Add some failure checks to prevent this.

Switch all embedders to use platform_strong.dill instead of platform.dill (the flutter_tester binary already does this) (#6024)

We'd like the ability to add Flutter to existing iOS applications
without requiring that they set `FLTLibraryPath` and `FLTAssetsPath`
in the main bundle's `Info.plist`.

1. Modify `-[FlutterDartProject initWithPrecompiledDartBundle:]` to
   support setting the library and assets path from the specified
   `NSBundle` instead.

2. If no `NSBundle` is explicitly specified, look for one with a
   default bundle identifier ("io.flutter.flutter.app") before
   falling back to the main NSBundle.

Also remove `+[FlutterDartProject pathForFlutterAssetsFromBundle:]`
because we don't use it internally, and it isn't exposed in the
header file.

Dart might choose to marshall the timestamps to a Java Long or Integer.
Casting directly to int was crashing when the timestamp wass a Long.

This allows the framework to know that a frame with the resized view is
ready and to behave deterministically to workaround the jank issue
described in flutter/flutter/19572

This is needed to avoid jank when resizing an embedded Android view.
See
https://github.com/flutter/flutter/issues/19572#issuecomment-410400724

* Updated DartCallbackCache to write callback cache to disk which is
restored on engine startup
* Ensure cache isn't moved off disk in iOS

* Reland "Updated background execution implementation for Android" w/ JNI fixes for merge breakages

This reverts commit 5442c0a7.

This reverts commit bc885f31.

* Flush all embedded Android view on hot restart.

Adds an OnEngineRestarted method to PlatformView, this is currently only
implemented for Android where we need to use it for embedded views.

* review comments followup

* rename to OnPreEngineRestart, call before Clone

Instead, send them with the new unknown PointerDeviceKind.

We hit this when running `adb shell input tap` in tests which sends events with
an unknown tool type.

This also fills in a missing conversion for TOOL_TYPE_ERASER.

* Add an explicit `-[FlutterViewController init]` implementation

`-[FlutterViewController init]` currently works because it inherits
the `-[UIViewController init]` convenience initializer that invokes
the `-[UIViewController initWithNibName:bundle:]` designated
initializer that `FlutterViewController` overrides.

However, this doesn't seem to be explicitly documented, so it's a bit
confusing (or at least non-obvious), and it seems potentially
brittle.  Add an explicit implementation of `-[FlutterViewController
init]` instead.