* fixing the autofill overlay problem (blue area for chrome)

* addression comments

Preserve specified AssetResolvers when performing a hot restart or updating the asset directory (#21611)

Follow up from #21436 . That PR works for all embeddings except for Android, which creates a special JNI AssetResolver. Since the shell cannot recreate this resolver, update the logic to preserve existing resolvers instead.

Neither of these methods mutate the state of the model.

This reverts commit 02324994.

Previously, the selection base and extent were stored internally as
iterators over text_. Since iterators must be treated as invalidated
whenever the underlying container changes, this requires that
selection_base_ and selection_extent_ be re-assigned after every change
to text_.

This is not currently particularly problematic, but once we add fields
to track the base and extent of the composing region for multi-step
input method support, as well as support for the sub-range within the
composing region to which edits/completions apply, we end up having to
regenerate a lot of iterators with each change, many of which are
logically unchanged in position.

A side benefit is that this simplifies inspection of these fields when
debugging.

This is similar to the workaround used for
https://github.com/flutter/flutter/issues/30347

The Minikin line breaker inserts greedy breaks based on a comparison of
postBreak width and currentLineWidth.  currentLineWidth is provided by
the framework based on previous calls to Layout::measureText.
That calculation may not exactly match the calculation of postBreak.

This change ensures that breaks are only added if the difference
between postBreak and currentLineWidth is significant.

Fixes https://github.com/flutter/flutter/issues/65419

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/fuchsia-mac-sdk-flutter-engine
Please CC liyuqian@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/+doc/master/autoroll/README.md

https://skia.googlesource.com/skia.git/+log/107114dd1d6e..a7f69c290667

*** Force-landing this with red checks so we don't fall too far behind. (All failures are flakes).

2020-10-07 egdaniel@google.com Add stencil formats to all the backends.
2020-10-07 brianosman@google.com Only include one variable per declaration statement
2020-10-07 johnstiles@google.com Remove accidentally repeated bit-index expression.
2020-10-07 mtklein@google.com refactor HashAndEncode
2020-10-07 robertphillips@google.com Centralize CreateLazyView helper in GrThreadSafeUniquelyKeyedProxyViewCache
2020-10-07 michaelludwig@google.com Update AutoLayerForImageFilter to use SkTCopyOnFirstWrite
2020-10-07 johnstiles@google.com Rename ChunkBits to kChunkBits.
2020-10-07 jvanverth@google.com Revert "Add a 2d cross product intrinsic to sksl"
2020-10-07 robertphillips@google.com Add customData capability to the thread-safe proxy cache ...
2020-10-07 johnstiles@google.com Fix data() method and add unit test.
2020-10-07 kjlubick@google.com [canvaskit] Add make rule to check types
2020-10-07 csmartdalton@google.com Add a 2d cross product intrinsic to sksl
2020-10-07 skia-autoroll@skia-public.iam.gserviceaccount.com Roll SwiftShader from afe6ca45b6da to 635de036d766 (3 revisions)
2020-10-07 skia-autoroll@skia-public.iam.gserviceaccount.com Roll ANGLE from 77e3d0ae97b6 to 3df629c55d89 (20 revisions)
2020-10-07 skia-autoroll@skia-public.iam.gserviceaccount.com Roll Chromium from 4259b6b6cb0f to 3c77521707c0 (463 revisions)
2020-10-07 skia-autoroll@skia-public.iam.gserviceaccount.com Roll Dawn from 326e14f34bb5 to 7e22b1c44fb0 (6 revisions)
2020-10-07 mtklein@google.com retry³ absl
2020-10-06 johnstiles@google.com Separate out SymbolTable aliases from regular Symbols.

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC jvanverth@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/+doc/master/autoroll/README.md

hasStrings method for clipboard status, Linux

* running web tests only on DEPS and web directories

* adding more folders to skip tests

Adds the ability to pass engine switches temporarily at runtime via
environment variables. Uses the same approach recently added to
Windows and macOS.

This is enabled only for debug/profile to avoid potential issues with
tampering with released applications, but if there is a need for that in
the future it could be added (potentially with a whitelist, as is
currently used for Dart VM flags).

Fixes flutter/flutter#60393

Previously, TextInputModel's SetEditingState method was a 1:1 mapping of
the underlying protocol used on the text input channel between the
framework and the engine. This breaks it up into two methods, which
allows the selection to be updated independently of the text, and avoids
tying the API the the underlying protocol.

This will become more important when we add additional state to support
composing regions for multi-step input methods such as those used for
Japanese.

SetText resets the selection rather than making a best-efforts attempt
to preserve it. This choice was primarily to keep the code simple and
make the API easier to reason about. An alternative would have been to
make a best-effort attempt to preserve the selection, potentially
clamping one or both to the end of the new string. In all cases where an
embedder resets the string, it is expected that they also have the
selection, so can call SetSelection with an updated selection if needed.