This rewrites the sample code analysis script to be a little less of a hack (but still not pretty), and to handle snippets as well.

It also changes the semantics of how sample code is handled: the namespace for the sample code is now limited to the file that it appears in, so some additional "Examples can assume:" blocks were added. The upside of this is that there will be far fewer name collisions.

I fixed the output too: no longer will you get 4000 lines of numbered output with the error at the top and have to grep for the actual problem. It gives the filename and line number of the original location of the code (in the comment in the tree), and prints out the source code on the line that caused the problem along with the error.

For snippets, it prints out the location of the start of the snippet and the source code line that causes the problem. It can't print out the original line, because snippets get formatted when they are written, so the line might not be in the same place.

This stops reading from pipe-to-file log after the build is completed. Attempting to read from pipe-to-file keeps open blocked because nobody is going to write into that pipe.

It's not usual for this not to be set, but it affected at least one user (#23909) and there are a non-zero number of people online saying it's not set. It's better that we don't crash.

Fixes #23909.

`RenderEditable.paint` assumes that if the length of the text fits within the
visible region, then the text will be rendered at the start of the region and be
completely visible. This is not always true, since the text may still be
rendered at an offset if an animation is ongoing when the text begins to fit.

This fixes #22288 and #14121

* Update `osx_instance`

Cirrus no longer supports `high-sierra-xcode-9.4`.

* Makes FlexibleSpaceSettingsPublic and adds a test

This reverts commit 76a1abd4.

* Adds functionality for progress indicator height to be controlled by the parent.

See https://github.com/flutter/flutter/issues/17910

https://github.com/flutter/engine/compare/e91e4db7e03d...88cb78cdf62c

git log e91e4db7e03d..88cb78cdf62c --no-merges --oneline
88cb78cdf Roll src/third_party/skia 13853a120d5a..30edaaac1da4 (1 commits) (flutter/engine#6732)
eacf61efd Roll src/third_party/skia 2dc1e34f9029..13853a120d5a (1 commits) (flutter/engine#6731)
7618e5447 Roll src/third_party/skia 26fcd7166c74..2dc1e34f9029 (2 commits) (flutter/engine#6730)
10ec1fd6b Roll src/third_party/skia 94d7af7bcc96..26fcd7166c74 (5 commits) (flutter/engine#6729)
9e1f546a8 Add an overlay surface on top of embedded UIViews. (flutter/engine#6726)
136055669 Roll src/third_party/skia e978ca297965..94d7af7bcc96 (5 commits) (flutter/engine#6727)
c57d29ab6 Fixed typo (flutter/engine#6717)
f3fcb8f01 Roll src/third_party/skia f1eda00bf6b0..e978ca297965 (10 commits) (flutter/engine#6725)
fbb7893a0 Report asset names in loading trace events. (flutter/engine#6713)
d06ace699 Roll src/third_party/skia 3bdaa46bff71..f1eda00bf6b0 (11 commits) (flutter/engine#6724)
60d4d582f Roll src/third_party/skia 763fc966993d..3bdaa46bff71 (2 commits) (flutter/engine#6723)


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So we're sure that:
1. We won't break the API by not allowing to mutate fields
2. We won't forget to markNeedsAddToScene after mutation

These tests have been run for a few days now with no flakiness.

This is needed to run flutter app on multiple iOS devices at a time.

This reverts commit 949cfcf1.

beautified Readme , removed bullet

* Use maybePop in place of pop in ModalBarrier

https://github.com/flutter/engine/compare/c79faed71c66...e91e4db7e03d

git log c79faed71c66..e91e4db7e03d --no-merges --oneline
e91e4db7e Roll src/third_party/skia e008d6feb2d0..763fc966993d (1 commits) (flutter/engine#6722)
28514b524 Roll src/third_party/skia 1ae419b62b2b..e008d6feb2d0 (1 commits) (flutter/engine#6721)
b9726c240 Roll src/third_party/skia 628f0a57d102..1ae419b62b2b (2 commits) (flutter/engine#6720)
1b0d26a92 Roll src/third_party/skia d7a7586b0d2f..628f0a57d102 (1 commits) (flutter/engine#6718)


The AutoRoll server is located here: https://autoroll.skia.org/r/flutter-engine-flutter-autoroll

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https://github.com/flutter/engine/compare/0ec3b7d437d4...c79faed71c66

git log 0ec3b7d437d4..c79faed71c66 --no-merges --oneline
c79faed71 Decode UIView's creation parameters and pass them to the view factory. (flutter/engine#6715)
467ff33aa Roll src/third_party/skia 348a03729796..d7a7586b0d2f (12 commits) (flutter/engine#6714)


The AutoRoll server is located here: https://autoroll.skia.org/r/flutter-engine-flutter-autoroll

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If the roll is causing failures, please contact the current sheriff, who should
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https://github.com/flutter/engine/compare/d9c2b215abda...0ec3b7d437d4

git log d9c2b215abda..0ec3b7d437d4 --no-merges --oneline
0ec3b7d43 Apply changes to the embedded UIView tree when presenting a frame (flutter/engine#6712)
92944f72f Move FlutterPlatformViewsController into FlutterEngine. (flutter/engine#6709)
d34cb1757 Roll src/third_party/skia 9985a27c06ad..348a03729796 (15 commits) (flutter/engine#6710)
a27d2f2bc Check needs_painting in RasterCache::Prepare (flutter/engine#6708)
552fae60c Roll src/third_party/skia 83d923f38664..9985a27c06ad (2 commits) (flutter/engine#6707)
67ba69717 Roll src/third_party/skia 4d8f48db9ef5..83d923f38664 (2 commits) (flutter/engine#6706)
54882ef86 Roll src/third_party/skia 69a72945dcdd..4d8f48db9ef5 (1 commits) (flutter/engine#6705)
635e20498 Roll src/third_party/skia 1801b94e85b4..69a72945dcdd (1 commits) (flutter/engine#6704)
059876ea9  Delay embedded UIViews touch events until the framework says so. (flutter/engine#6665)
605ae5d88 Roll src/third_party/skia 4c169456061d..1801b94e85b4 (2 commits) (flutter/engine#6703)
d8672baaa Ensure Simulator publishes mDNS records (flutter/engine#6696)


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* Adds DropDownFormField Convenience Class

* Use Xcode build configurations to drive Flutter build mode

* Proper check wrt local_engine, print error if profile mode misisng

* Remove unused code, update tests, fix template problem, update warning

* fix up warning

* add explanatory dev comment

* fix whitespace

* missing words, change lambda arrow to function body

* error indentation

* Test early exits for xcode_backend.sh

* only on macOS, use right test

* Update error messages

* case insensitive compare for build config

* Update gallery podfile

* update projects to add profile configuration

* make compatible with flavors

* add missing plist files

* add FLUTTER_FRAMEWORK_DIR back, set swift version for profile, tell Podfile about profile

* Adds drawer state query functions

Re-landing #23412 with a fix to the PlatformLayer's addToScene signature.

#23412 was broken by the change to Layer done in #23434.

It seemed green as the presubmits were done before #23434 was landed, and when #23412 landed it broke the build.

Reverts #23779