Relands #17489 with a fix for the unit test flake.

The previous unit test relied on the new instance not being created at the same memory address, which isn't guaranteed.

Added "unrecognized-selector" errors to match g3 builds, added
"overriding-method-mismatch" to catch a common error.

The transitive dependency on the embedder library brings in the right
runtime for the build mode, so directly depending on the JIT version
isn't necessary, and causes duplicate symbol issues in release builds.

* remove the fake reply for paste message. the clipboard.dart will reply with the content of the clipboard

* also remove the fake answer for copy

I fixed a bug that left a blank at the bottom of the screen when the iPad's split keyboard was hidden.

I also had the same problem with this issue, so I fixed it.
iPad split keyboard cause a blank space problem

There is no function to change the space size at the bottom of the screen when the split keyboard is moved. This is because it's not clear what the keyboard should do when it's moved to the top of the screen.

Previously the build scripts obtained the lambda support classes from rt.jar,
which is no longer provided by recent versions of the JDK.

flutter/flutter#54022

The original issue is the _MotionEventsDispatcher depends on all down pointers to send out their own move events. If the third pointer has the movement of zero, it will get filter out by the PointerDataPacketConverter. This result with only two pointer move events been sent to RenderAndroidView, and they both get ignored because it is waiting for the third one.

This pr fixes it by always forward the move event

https://dart.googlesource.com/sdk.git/+log/275a76f2fcd8..dcdc71d7639a

git log 275a76f2fcd8..dcdc71d7639a --date=short --first-parent --format='%ad %ae %s'
2020-04-07 scheglov@google.com Report CONFLICTING_GENERIC_INTERFACES using ClassHierarchy.
2020-04-07 eernst@google.com Adjust member signature expectations for mixed inheritance
2020-04-07 kustermann@google.com [vm/compiler] Move runtime call of Throw/ReThrow/AssertBoolean/InstanceOf out into a Stub
2020-04-07 cskau@google.com [Compiler] Adds a set of generic AllocateObject stubs.
2020-04-07 scheglov@google.com Update constants_2018/constant_types_test to allow type parameters in 'as'.
2020-04-07 alexmarkov@google.com [vm/tests] Speed up / filter slow vm/dart/minimal_kernel*_test
2020-04-07 leafp@google.com Add tests for extended GLB.
2020-04-07 sra@google.com [dart2js] createFromStaticType for LegacyType
2020-04-07 rnystrom@google.com Migrate language_2/covariant to NNBD.
2020-04-07 srujzs@google.com [dart:html] Fix named args in js_typed_interop tests
2020-04-06 rnystrom@google.com Migrate language_2/constants_2018 to NNBD.
2020-04-06 scheglov@google.com Update language/constructor/return_test
2020-04-06 scheglov@google.com Update ClassHierarchy for legacy support, record errors.
2020-04-06 rmacnak@google.com Revert "[vm, gc] Parallel scavenge."
2020-04-06 srujzs@google.com [dart:html] Add nullability to item type for lists
2020-04-06 srujzs@google.com [dart:html] Remove 2.7 annotation from lib/html
2020-04-06 srujzs@google.com [dart:html] Migrate tests with only null asserts
2020-04-06 srujzs@google.com [dart:html] Migrate tests that need changes to NNBD
2020-04-06 srujzs@google.com [dart:html] Migrate more js tests to NNBD
2020-04-06 srujzs@google.com [dart:html] Migrate html tests with dynamic list conversions
2020-04-06 srujzs@google.com [dart:html] Migrate htmlcollection_test to null-safe
2020-04-06 rmacnak@google.com [vm, gc] Parallel scavenge.
2020-04-06 jwren@google.com Update the completion_metrics.dart algorithm to have 2 overlay options
2020-04-06 scheglov@google.com Clear class hierarchies to reduce memory consumption.
2020-04-06 rileyporter@google.com [tests] Removing more List constructor usage in corelib tests.
2020-04-06 liama@google.com [vm] Fix bug in late field reloading
2020-04-06 mfairhurst@google.com [nnbd_migration] Add sanity checks before writing to disk.
2020-04-06 mfairhurst@google.com [nnbd_migration] Change edit links to buttons.
2020-04-06 mehmetf@google.com Reland "[dart:_http] Allow the embedder to prohibit HTTP traffic."
2020-04-06 rmacnak@google.com [vm] Include the handler function in HandleMessage timeline events.
2020-04-06 scheglov@google.com Allow potentially constant type expression in 'as'.

Created with:
  gclient setdep -r src/third_party/dart@dcdc71d7639a

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/dart-sdk-flutter-engine
Please CC dart-vm-team@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

Bug: None
Tbr: dart-vm-team@google.com

Test failure:

    [ RUN      ] FlutterStringCodec.CanEncodeAndDecodeNil
    2020-04-07 10:21:25.091 flutter_channels_unittests[26965:163315] *** Assertion failure in -[FlutterStringCodec encode:], ../../flutter/shell/platform/darwin/common/framework/Source/FlutterCodecs.mm:36
    2020-04-07 10:21:25.118 flutter_channels_unittests[26965:163315] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: ''
    *** First throw call stack:
    (
    	0   CoreFoundation                      0x00007fff2ccabcf9 __exceptionPreprocess + 256
    	1   libobjc.A.dylib                     0x00007fff5785ea17 objc_exception_throw + 48
    	2   CoreFoundation                      0x00007fff2ccc6a16 +[NSException raise:format:arguments:] + 98
    	3   Foundation                          0x00007fff2ef58e11 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 194
    	4   flutter_channels_unittests          0x0000000105f1cce2 -[FlutterStringCodec encode:] + 290
    	5   flutter_channels_unittests          0x0000000105f01bbb _ZN45FlutterStringCodec_CanEncodeAndDecodeNil_Test8TestBodyEv + 107
    	6   flutter_channels_unittests          0x00000001081d1732 _ZN7testing8internal38HandleSehExceptionsInMethodIfSupportedINS_4TestEvEET0_PT_MS4_FS3_vEPKc + 146
    	7   flutter_channels_unittests          0x00000001081a76b0 _ZN7testing8internal35HandleExceptionsInMethodIfSupportedINS_4TestEvEET0_PT_MS4_FS3_vEPKc + 128
    	8   flutter_channels_unittests          0x00000001081a75c1 _ZN7testing4Test3RunEv + 209
    	9   flutter_channels_unittests          0x00000001081a8415 _ZN7testing8TestInfo3RunEv + 229
    	10  flutter_channels_unittests          0x00000001081a95aa _ZN7testing9TestSuite3RunEv + 266
    	11  flutter_channels_unittests          0x00000001081b4e43 _ZN7testing8internal12UnitTestImpl11RunAllTestsEv + 995
    	12  flutter_channels_unittests          0x00000001081d8572 _ZN7testing8internal38HandleSehExceptionsInMethodIfSupportedINS0_12UnitTestImplEbEET0_PT_MS4_FS3_vEPKc + 146
    	13  flutter_channels_unittests          0x00000001081b49b3 _ZN7testing8internal35HandleExceptionsInMethodIfSupportedINS0_12UnitTestImplEbEET0_PT_MS4_FS3_vEPKc + 131
    	14  flutter_channels_unittests          0x00000001081b4835 _ZN7testing8UnitTest3RunEv + 197
    	15  flutter_channels_unittests          0x0000000105f22e73 _Z13RUN_ALL_TESTSv + 35
    	16  flutter_channels_unittests          0x0000000105f22d79 main + 553
    	17  libdyld.dylib                       0x00007fff5908c3d5 start + 1
    )
    libc++abi.dylib: terminating with uncaught exception of type NSException
    [ERROR:flutter/fml/backtrace.cc(110)] Caught signal SIGABRT during program execution.
    Frame 0: 0x7fff591316a6 abort
    Frame 1: 0x7fff560ea641 __cxa_bad_cast
    Frame 2: 0x7fff560ea7df default_unexpected_handler()�
    Frame 3: 0x7fff57860ee3 _objc_terminate()�
    Frame 4: 0x7fff560f619e std::__terminate(void (*)())�
    Frame 5: 0x7fff560f5f86 __cxa_get_exception_ptr
    Frame 6: 0x7fff560e8f99 __cxa_get_globals
    Frame 7: 0x7fff5785eb51 objc_exception_throw
    Frame 8: 0x7fff2ccc6a16 +[NSException raise:format:arguments:]
    Frame 9: 0x7fff2ef58e11 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:]
    Frame 10: 0x105f1cce2 -[FlutterStringCodec encode:]
    Frame 11: 0x105f01bbb FlutterStringCodec_CanEncodeAndDecodeNil_Test::TestBody()�
    Frame 12: 0x1081d1732 void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*)�
    Frame 13: 0x1081a76b0 void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*)�
    Frame 14: 0x1081a75c1 testing::Test::Run()�
    Frame 15: 0x1081a8415 testing::TestInfo::Run()�
    Frame 16: 0x1081a95aa testing::TestSuite::Run()�
    Frame 17: 0x1081b4e43 testing::internal::UnitTestImpl::RunAllTests()�
    Frame 18: 0x1081d8572 bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*)�
    Frame 19: 0x1081b49b3 bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*)�
    Frame 20: 0x1081b4835 testing::UnitTest::Run()�
    Frame 21: 0x105f22e73 RUN_ALL_TESTS()�
    Frame 22: 0x105f22d79 main
    Frame 23: 0x7fff5908c3d5 start

This reverts commit d1c90b42.

Seems to have triggered flaky failures on the Windows bot since landing.
Example failure:

    [ RUN      ] PluginRegistrarTest.ManagerRemovesOnDestruction
    c:\b\s\w\ir\cache\builder\src\flutter\shell\platform\common\cpp\client_wrapper\plugin_registrar_unittests.cc(149): error: Expected: (manager->GetRegistrar<PluginRegistrar>(dummy_registrar_handle)) != (first_wrapper), actual: 000002400A90E3D0 vs 000002400A90E3D0

This reverts commit faf44fed.

"unrecognized-selector" and "overriding-method-mismatch" added as errors.

This reverts commit 4b69cf2c.

Fuchsia is the main consumer of these CIPD packages and - to simplify
its infrastructure - it is migrating its SDK partners over to producing
a CIPD package containing a flat .build-id directory.

This change also updates the CIPD package so that the .build-id
directory is placed at the root.

Bug: fxbug.dev/41443

This makes two changes:
- Adds a way to register a callback for when a FlutterDesktopPluginRegistrarRef is destroyed, and implements the logic to call it in the Windows and Linux embeddings.
- Adds a class to the C++ wrapper that handles making a singleton owning PluginRegistrar wrappers, and destroying them when the underlying reference goes away, to avoid needing that boilerplate code in every plugin's source.

Fixes https://github.com/flutter/flutter/issues/53496