This patch just fixes the next and previous buttons to be in the proper
place. There might be other issues with the DatePicker, but this one was
obvious.

See #11377

This roll caused performance regressions in benchmarks:
* complex_layout_scroll_perf
* flutter_gallery_transition_perf

This reverts commit f430a45a.

* Roll engien to 79332e5c42555875c7070c33810dab3f0012ace1

* Remove deprecated @proxy

* Roll engine to ceb6d05c2fb3bd5c31a25d4b08be9fd97b55a446

Checksum validation is intended only as a performance improvement.
Checksum de-serialization errors (typically framework version mismatch) are
expected on framework updates and shouldn't be user-visible except for
informational purposes when --verbose is set.

ios-deploy 1.9.2 includes fixes for a common source of Xcode breakage
(flutter/flutter#4326) with Xcode 8.3.3 + iOS 10.3.3, and is required to
to support Xcode 9 (flutter/flutter#11875).

Opening Xcode is no longer sufficient to enable develop mode in Xcode 9.
Update the message to run the command-line tool. Alternatively users can
launch an app in the Xcode debugger to do this.

* getOffsetToReveal deals with pinned slivers

If a Sliver can potentially be pinned at the edge of a viewport, getOffsetToReveal will take that into account and scroll further up/down to ensure that the object to reveal doesn't end up covered by a pinned sliver.

This is important for accessibility scrolling with app bars.

Since how much a pinned sliver is covering is dynamic (it can change with scroll offset, etc), getOffsetToReveal deals with the worst case and tries to ensure that the object to uncover is visible when the pinned slivers are at their max pinned extent.

* name fixes

* review feedback

* typos

* renaming

* fix analyzer

* fix test

* analyzer fixes

Fixes #11855

Adds the app entrypoint as a key in the checksum file.

This change eliminates the assumption that checksummed files change when
the main entrypoint changes. In the case where there are two
entrypoints, a.dart and b.dart and a.dart imports b.dart and b.dart
imports a.dart, building the app with entrypoint a.dart followed by a
build of the app with entrypoint b.dart would result in the same
files list and checksums, but should invalidate the build.

* Move host build check until it's actually used

* Elaborate diagnostic message

Fixes #11868

Fixes #11848

Also, fix the interpolation between visual and directional fractional
offsets. The interpolation now works visually in whatever direction the
result eventually gets resolved into.

Fixes #11847
Fixes #11357

* Fixed TrackingScrollController cleaning stored offset on position's detach

* Fixed format.

* Fixed format.

* Fixed test with Directionality support.

Fixes #11379

Fix a test for build invalidation due to a change in main entry point.
Previously this test's build was always invalidated to the the lack of a
previous snapshot (as well as the change in checksums). This change
ensures that the build is invalidated only due to the change in
checksums.

Most of the framework widgets should work in terms of EdgeInsetsGeometry
rather than EdgeInsets so that their clients can supply directional
insets.

* enable lint prefer_final_fields

* enable lint recursive_getters

* enable lint unnecessary_overrides

Fixes #5215

Fixes #11381

This reverts commit ec25f6bd.

* Fixed TrackingScrollController cleaning stored offset on position's detach

* Fixed format.

* Fixed format.

extract_messages script currently fails to parse this file because of its use of static asserts, super and a ctr body. Since we already have an assert in the body, I think it is also more readable to put all of them together. _LocalizationScope follows the same pattern above.

This patch migrates iOS device listing from using Xcode instruments to
using the libimobiledevice tools idevice_id and ideviceinfo.

ideviceinfo was previously incompatible with iOS 11 physical devices;
this has now been fixed.

In 37bb5f13 flutter_tools migrated from
libimobiledevice-based device listing on iOS to using Xcode instruments
to work around the lack of support for iOS 11. Using instruments entails
several downsides, including a significantly higher performance hit, and
leaking hung DTServiceHub processes in certain cases when a simulator is
running, necessitating workarounds in which we watched for, and cleaned
up leaked DTServiceHub processes. This patch returns reverts the move to
instruments now that it's no longer necessary.

* rename Element.visitChildrenForSemantics to debugVisitOnstageChildren

* address comments