* add the full path to a flutter command

* remove an unused import

* review comments

We were trying to only catch WebSocketException, but in fact
SocketException can be thrown as well.

This engine roll contains the following commits:

* flutter/engine@09d05a389: Prepare and run child isolates on a VM managed (i.e. no UI) task runner.
* flutter/engine@adee35142: Throw an error or return null if FlutterView.getBitmap fails

Fixes #13655

* log error when calling setState in constructor

Semantics object support for edge triggered semantics 

This chip demo is more interactive than the last one, trying to exercise all of the types of chips for a demo that lets you select different types of "chips" (like tortilla, wood, micro, etc.), and then filter them and select an action on them.

* Fine-tune iOS's scroll start feel

* remove negations in doc

* Our own dart-side gesture arena also contributes to the 'jerk'. Make sure that snap is accounted as well.

* Added more code comments from review.

Fixes #14590.

This moves --vm_snapshot_data and --isolate_snapshot_data argument
hardcoding from GenSnapshot (a minimal wrapper around gen_snapshot
invocations) to Snapshotter.buildScriptSnapshot(). These arguments are
present in both AOT and script snapshots, but differ semantically: for
script snapshots they're inputs from the host engine artifacts
directory, for AOT snapshots they're outputs to the build directory.

This is a PR giving some love to the abandoned PR #16263 by @harrisonturton

I've added a test, and formatted it to be readable.

Currently the CircleAvatar does not set a fit property on the DecorationImage it uses to paint images. This causes non-square images to not fully cover the circle, which looks pretty bad. This PR sets it to BoxFix.cover.

Fixes #13478.

We're seeing occasional test timeouts trying to call `FlutterDriver.connect()`.
Unfortunately, when the test is timed out at the test runner level, you don't
get a meaningful test failure or stack trace of where the timeout occurrred.
Your test harness also doesn't get to clean up, which can include things like
saving the device logs to see what was going on in the device.

Thus, this change adds timeouts in the places where we've most
commonly observed hangs during tests.

This roll includes the following commits.

* flutter/engine@637e921d6: Use the raster cache when rendering screenshots as bitmaps (#5050)
* flutter/engine@a23fa923c: Look for an assets path specification in the Info.plist. (#5049)

* update engine version, ignore scopesRoute and namesRoute flags until framework support is added

This contains the following commits:

flutter/engine@3cc8d82 Fix more Linux unittest targets.
flutter/engine@b6ba69b libtxt: add boxes representing empty lines in GetRectsForRange
flutter/engine@388f019 Enable downscale of very large images when uploading on IO thread
flutter/engine@22e1381 Allow runtime unit-test to perform dynamic symbol resolution for Dart snapshots.
flutter/engine@59d1366 Don’t build the host shell on target builds.
flutter/engine@7a6b779 Remove the weak pointer factory from the service isolate's DartIsolate object
flutter/engine@d4729ab Update the embedder GN target to use a source set instead of a complete static library.
flutter/engine@8973c73 Implement Scene::toImage for creating a raster image representation of a scene.
flutter/engine@572c584 Configure kernel paths in the embedder if the asset directory contains the kernel assets
flutter/engine@8ed932c Roll src/third_party/skia/ 1cd6098d5..1ccaa6e05 (20 commits)
flutter/engine@a0804f3 Simplify weak pointer factories and allow vending weak pointers on multiple threads.

Adding some tests for onTapDown and onTapCancel for the InkWell, as suggested in post-submission comments by @Hixie in #16190.

Also, added those to the diagnostic output.

* Run tests in dart2 mode.

* Fix type check

* Drop --checked, leave --preview-dart-2

* Remove debugging leftovers.

Support summary-details tree view.

This contains the following commits:

flutter/engine@5822b6e Clear the canvas when attempting to render to the surface.
flutter/engine@d8eb659 Make the rasterizer own the compositor context.
flutter/engine@387945c Correct ninja command instruction
flutter/engine@00911b2 Don't send platform messages to isolates that are not running.
flutter/engine@5c857ee Set the start timestamp in the contructor of the first shell.