Fix Windows embedding. Appears that #6523 or #6525 introduced a bug for embedder scenarios causing the window native library to be incorrectly initialized and thus incapable of correctly resolving GL functions.  This change fixes that. (#6624)

* Allow FlutterViewController to specify whether its FlutterView is opaque

According to the iOS docs, implementing
`- (id)insertDictationResultPlaceholder`

```Implementation of this method is optional but can be done when you want to provide a specific rectangle for the placeholder animation while the dictation results are being processed. ```

If you do not implement this method, UIKit will insert a default placeholder of 10 whitespace characters. By overriding this, no placeholder text will be inserted. If you implement the `insertDictationResultPlaceholder`, you must implement
`- (void)removeDictationResultPlaceholder:(id)placeholder willInsertResult:(BOOL)willInsertResult`

* Locale Passing

* Pass full locale list and script and variant codes to framework

* Working Android locale list passing and fallback

* Publish port of observatory over mDNS

* Fix crash when removeViewImmediate invoked from platform view

* Clear animation before remove view from mFakeWindowRootView

Updates buildroot to https://github.com/flutter/buildroot/pull/180.

Also check whether the implementation behind the resolver is OpenGL or
OpenGL ES

Add a `-[FlutterViewController setFlutterViewDidRenderCallback:]`
method on iOS so client applications can be notified when the Flutter
view has rendered.  This can be used for add2app cases to determine
when to take an initial screenshot for comparisons in automated
tests.

The callback is expected to be an Objective-C block (or Swift
closure).  I chose to support only a single callback because it's
much simpler (especially since it does not require a separate method
to unregister the callback), and it's not clear that there are use
cases that would justify additional complexity.  Clients have the
flexibility to make their callback invoke other callbacks anyway.

I alternatively considered adding a `-[FlutterViewController
viewDidRenderFirstFlutterFrame]` method that clients could override
in a subclass, but using an Objective-C block seems more flexible and
less of a burden.

Fixes https://github.com/flutter/flutter/issues/20665

Use an older version of SurfaceTexture.setOnFrameAvailableListener when running on pre-Lollipop devices (#6489)

Fixes https://github.com/flutter/flutter/issues/21730

* Missing dealloc method in FlutterEventChannel

* fix off by one

* add documentation on counting for setToIndex

This is discovered in the new Google3 checks. It should not block our
roll but it's nice to fix them.

Remove touch mapper and respect the UITouch phase when calculating the pointer data change type. (#6430)

The touch mapper was a relic of a time when the pointer IDs had to be less
than 16. Not respecting the touch phase is getting in the way of clients that
fake their own touches. Turns out the AppDelegate also like to fake touches to
simulate status bar events. Now, except in cases where there is a specific
override in place, the UI touch phase is respected.

This works towards resolving https://github.com/flutter/flutter/issues/19888.

This further addresses https://github.com/flutter/flutter/issues/14568.

* SystemNavigator.pop can pop w/o UINavigationController

* Fix a compilation problem when  using iPhoneOS12.0sdk(Xcode10).

Also teaches FML to create files and directories.

This will not be active on the Framework until https://github.com/flutter/flutter/pull/22221 lands.

Format code from previous patch

* If isolate is already running, return true

* Use shell::Engine::RunStatus as result of Engine::Run

Use a screen height ratio to determine if the keyboard is onscreen or not. This is used because Android does not provide a deterministic API to detect this.

We remove the padding when the keyboard is closed and the inset is due to the hidden navigation bar, otherwise, we apply the full keyboard inset.

* Change FlutterDartProject to keep precedence when looking for the assets bundle

* Change assetsPath to fallback to mainBundle when the defined bundle does not contain assets

This shell used to serve the dual purpose of running Flutter tests as
well as optionally being able to run Flutter applications on a Mac
desktop. After all the test runner targets were consolidated
(flutter_tester), this target was no longer used to run the tests. This
target is currently only used by engine developers to test changes
quickly on the host. Even for this purpose, the Desktop embedders are
more full featured and use the stable embedder API. The presence of a
cross-platform tester target, alternatives for Desktop targets that use
the stable embedder API and the fact that this target is no longer
tested, makes having this code in the source entirely redundant.