Roll src/third_party/dart 5ae5aff6406a..91a3ea89c8e4 (22 commits)

[skia-flutter-autoroll]

https://dart.googlesource.com/sdk.git/+log/5ae5aff6406a..91a3ea89c8e4

git log 5ae5aff..91a3ea8 --date=short --first-parent --format='%ad %ae %s'
2020-01-31 zichangguo@google.com Revert "[dart:io] Stop forcing lower case on HttpHeaders"
2020-01-31 jcollins@google.com Add path parsing to pub support.
2020-01-31 srawlins@google.com Load navigation programatically; use badges for edit counts; #40115
2020-01-31 kustermann@google.com [vm/compiler] Mark Box instructions as non-speculative (since the inputs are always unboxed values and dont need to be checked)
2020-01-31 vsm@google.com [dartdevc/nnbd] enable co19_2 tests for legacy mode
2020-01-31 jwren@google.com Initial RelevanceAnalyzer support in the completion_metrics.dart algorithm with an initial example implementation of RHSOfAsExpression
2020-01-31 kustermann@google.com [vm] Set Class::is_const() based on final fields instead of generative constructors (which can be shaken by TFA)
2020-01-31 sigmund@google.com Update check_nnbd_sdk to diff expectations directly in dart.
2020-01-31 vsm@google.com [dartdevc] use var for top-level
2020-01-31 fishythefish@google.com [dart2js] Use flags to choose between legacy/NNBD in RTI.
2020-01-31 nshahan@google.com [dartdevc] Add dart:io back to the sdk
2020-01-31 johnniwinther@google.com [cfe] Add new flags to AsExpression and IsExpression
2020-01-31 scheglov@google.com Check for correct overrides as the specification requires.
2020-01-31 sigmund@google.com Fix based64 decoder.
2020-01-31 fishythefish@google.com [dart2js] Update generic function subtyping.
2020-01-31 srawlins@google.com NNBD preview: Add 'view' links to Edit List; #40115
2020-01-31 brianwilkerson@google.com Enable always_declare_return_types in analysis_server
2020-01-31 brianwilkerson@google.com Enable empty_catches in analysis_server
2020-01-31 brianwilkerson@google.com Improve the fix for empty_catch
2020-01-31 zichangguo@google.com [dart:io] Stop forcing lower case on HttpHeaders
2020-01-31 zichangguo@google.com [vm] seperate error and unknown types for getStdioHandletype
2020-01-31 kustermann@google.com [vm/reload] Fix crash in scavneger / GC after reload on ia32

Created with:
gclient setdep -r src/third_party/dart@91a3ea89c8e4

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

[skia-flutter-autoroll]

Auto-roller completed checks. About to merge.