Revert "Reland Clang 11, Roll buildroot to 1bc40a5f916adb93d87e2a2230a0ec43db876c1c (#17457)" (#17464)

This reverts commit a4026cc9.

* Reland "Roll Clang to v11, roll buildroot to fe13f79dce4ce9aab3209f11988d825dcf580b4a, allow newly exported symbols (#17440)" (#17451)"

This reverts commit a870bc53.

* skip golden that is different on macos

* buildroot to 1bc40a5f916adb93d87e2a2230a0ec43db876c1c

Started clearing out the semantics information in Dart as well as deleting the AccessibilityBridge. (#17433)

Revert "Roll Clang to v11, roll buildroot to fe13f79dce4ce9aab3209f11988d825dcf580b4a, allow newly exported symbols (#17440)" (#17451)

This reverts commit 8d723aeb.

Roll Clang to v11, roll buildroot to fe13f79dce4ce9aab3209f11988d825dcf580b4a, allow newly exported symbols (#17440)

* Buildroot to fe13f79dce4ce9aab3209f11988d825dcf580b4a

* whitelist more symbols

API staging is complete - these defines have been removed.

Fixes https://github.com/flutter/flutter/issues/18208. All Metal for iOS related work items described in https://github.com/orgs/flutter/projects/5 have been completed.

If the application says there is a new texture but does not provide one, reuse the last texture. (#17437)

This matches the behavior of the OpenGL backend.

We were always scaling z by 0, instead of 1. This
caused the z elevation of some layers to be 0,
which was incorrect.

Now that client apps use the same elevations on
Fuchsia and other platforms, shadows should look
identical.

Matches the structure used on Windows of assuming a directory format.

The following issues have been filed to track the handling of these enum values:

* Handle the UITouchTypeIndirectPointer enum value. https://github.com/flutter/flutter/issues/53696
* Handle the UITouchPhaseRegion enum values. https://github.com/flutter/flutter/issues/53695

No change in functionality. Only makes the iOS engine build on the latest
versions of Xcode and iOS SDK. The enum values cannot be used with the
API_AVAILABLE macro because the buildbots have not been updated yet.

Since the trace provider hasn't been created yet, it is not possible to
trace the creation of a trace provider using a TRACE_DURATION event (the
trace enabled and category check will always fail).  While this isn't
causing any urgent problems, remove it to set a good example for other
clients of tracing that might happen to reference this code.

Make the test robust even if the json map reorders its keys.

This PR touches variable names, class names, and file names so it's significantly more risky than its predecessor https://github.com/flutter/engine/pull/17329

Due to file name changes, this PR is expected to change the license files.

We haven't rename `shell/gpu` to `shell/raster` yet. It should be optional but I think it's better to have `raster_surface_software.cc` than `gpu_surface_software.cc`.

https://dart.googlesource.com/sdk.git/+log/11d6bc605512..e8c4aed700f5

git log 11d6bc605512..e8c4aed700f5 --date=short --first-parent --format='%ad %ae %s'
2020-03-31 scheglov@google.com Remove implementedForMixing from inheritance manager.
2020-03-31 scheglov@google.com Fix for crash in WrapInText when the parameter is not InterfaceType.
2020-03-31 rnystrom@google.com Migrate language_2/compile_time_constant to NNBD.
2020-03-31 alexmarkov@google.com [vm/nnbd] Do not treat late final fields as immutable
2020-03-31 lrn@google.com Add specialized classes for ZoneFunction<Function> to handle generics.
2020-03-31 sstrickl@google.com [vm] Check the global object pool (if any) when visiting functions.
2020-03-31 jensj@google.com [CFE] Add "annotate lines" option to parser suite
2020-03-31 sortie@google.com [dart:_http] Fix HeaderValue.parse if valueSeparator is parameterSeparator.
2020-03-31 sigurdm@google.com Bump pub revision
2020-03-31 kustermann@google.com [infra] Update tools/test.py and test matrix for running tests with arm64-qemu
2020-03-31 athom@google.com [co19] Roll co19 to 9934d8540d097366287267519413e888a7f6a482
2020-03-31 dmitryas@google.com [cfe] Apply the special treatment of FutureOr in GLB for NNBD
2020-03-31 karlklose@google.com [infra] Remove unused bot script
2020-03-31 jensj@google.com [CFE] Perform transformPostInference when doing expression compilation
2020-03-31 karlklose@google.com [infra] Remove creation of unused file
2020-03-31 asiva@google.com [Tests] Skip debugger_location_test (see https://github.com/dart-lang/sdk/issues/41219)
2020-03-31 rnystrom@google.com Migrate language_2/canonicalize to NNBD.
2020-03-30 srujzs@google.com [dart:html] Add bool type to supportsTypedData
2020-03-30 scheglov@google.com Deprecate isProxy / isOrInheritsProxy in ClassElement.
2020-03-30 scheglov@google.com Set dynamic resolution for super MethodInvocation in invalid context.

Created with:
  gclient setdep -r src/third_party/dart@e8c4aed700f5

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

* Add test to make sure we don't regress treeshaking of debugFillProperties
* update cirrus