* Apply transform to textures on android 

Add support for --strong option in the engine, create a strong mode version of the platform file (#4504)

* Add a --strong option to the front end server so we can use strong mode with preview-dart-2.

* Plumb the --strong option through the dart controller into the VM.

* - Build a strong version of platform.dill for use with the engine.
- Fix a strong mode static error in the assert statement

* Enable asserts when running debug version even in strong mode.

* Use the correct platform dill file for linking when doing the aot builds.

* Fix formatting issue.

This reverts commit 368380cf.

This breaks Flutter external_ui test.

* Revert "Revert "Fix filename handling for Windows. (#4482)" (#4484)"

This reverts commit 929e5b39.

Reverting now since issue with
gen_snapshot(as described in https://github.com/flutter/flutter/issues/13708) was fixed.

* resolve->resolveUri, drop underscores

* Fix underscore

* Apply transform to textures on android

* Remove mention of adb from instructions

This isn't a step we have our users do, so best that we don't do it either.

* Update CONTRIBUTING.md

This reverts commit eee4a1ed.

Original commit caused external_ui integration test failure on Android.

* Roll dart

* Update license

This adds a ClipboardPtr to RuntimeHolder that is used to handle
Clipboard.setData and Clipboard.getData.

This rule forces a build of the Dart SDK with the current host toolchain, which isn't needed.

* Apply transform to textures on android

* Use RAII canvas save

This caused a breakage on mac due to inconsistent signatures for
declaration and implementation.

* Adjust PhysicalModelLayer to use an abstract shape, and provide concrete RRect and Path shape implementations

* add a pushPhysicalShape to scene_builder and compositing.dart

This reverts commit 1fb58581.

This change is not sufficient as it exposes problem with kernel-based
gen_snapshot on Windows and results in Flutter test failures.

* Fix filename handling for Windows.

Bug: https://github.com/flutter/flutter/issues/13708

* Fix tyop

* Add final to make analyzer happy

Fixes https://github.com/flutter/flutter/issues/12377.

Revert "libtxt: Restore code that had been disabled due to older versions of ICU and HarfBuzz (#4456)" (#4474)

This reverts commit 503999ff.

Fuchsia is still pinned to ICU version 57, which doesn't have these APIs

* Roll Skia and remove PngPixelSerializer

* Update licenses

The engine build bots and engine development team now rely solely on
Xcode 9 to build the engine. The iOS 11 SDK is required (though we build
with deployment target of iOS 8) for several features such as safe area
inset support.