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If //ignore is bad, ignoring something for a whole file is presumably worse.

For #20483

The tool was failing if we had 2 separate non-canonical paths to the
same canonical paths.

flutter_tools cannot depend on flutter_goldens (as flutter_goldens
depdends on the Flutter sdk), so this commit splits client.dart from
flutter_goldens to a pure-dart flutter_goldens_client package.

The test places an embedded Android view at the top left, and verifies
that motion events that get to FlutterView are equivalent to the
synthesized motion events that gets to the embedded view.

See the README.md for more high level details.

* `flutter analyze` cleanup

* Make `--dartdocs` work in all modes.
* Make `analyze-sample-code.dart` more resilient.
* Add a test for `analyze-sample-code.dart`.
* Minor cleanup in related code and files.

* Apply review comments

* Fix tests

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* Allow option switches to have keys

* Review comments

Turns out we weren't deleting the dill directory or the fonts directory.

* Fixes resulting from audit of issues links

I looked at every link to GitHub in our repo. For cases where we had a TODO that was waiting for a bug to be fixed, and the bug has now been fixed, I applied the pending change. For cases where the link was out of date, I updated the link.

* Update run_test.dart

skip this test again since it failed on linux and macos bots

* Revert "Deprecated CupertinoDialog in favor of a new widget called CupertinoP… (#20649)"

This reverts commit 3a4ae280.

* Revert "Feature pesto new recipes (#19415)"

This reverts commit e2f3b3d6.

* Revert "Use markdown table (#20721)"

This reverts commit 82d43b95.

* Revert "Documentation regarding tap gesture callbacks (#20647)"

This reverts commit 3acc2785.

* Revert "Add branch to footer information in flutter docs (#20711)"

This reverts commit 9118d3d7.

* Revert "Performance test cleanup (#20652)"

This reverts commit 1993a673.

* Revert "Track number of package dependencies in Flutter (#20722)"

This reverts commit 03d6f18f.

Deprecated CupertinoDialog in favor of a new widget called CupertinoPopupSurface. (#20397)

<img width="273" alt="pesto_before" src="https://user-images.githubusercontent.com/13839358/43009716-64b6d726-8c0c-11e8-989a-13eaff72ccee.png">
<img width="273" alt="pesto_after" src="https://user-images.githubusercontent.com/13839358/43009717-66074a34-8c0c-11e8-92ae-f5fb4074f43a.png">

* Fix TODO syntax.
* Clarify messages for some timeouts, to aid debugging.
* Increase some other timeouts that were a needlessly short, to reduce sources of flakes.
* Remove some more timeouts that were mostly redundant, to remove complexity.
* Minor style cleanup.
* Remove some dangerous traps (specifically, hide the explicit start/end times in TimedEvent since they shouldn't matter).

All temporary directory start with `flutter_` and have their random component separated from the name by a period, as in `flutter_test_bundle.YFYQMY`.

I've tried to find some of the places where we didn't cleanly delete temporary directories, too. This greatly reduces, though it does not entirely eliminate, the directories we leave behind when running tests, especially `flutter_tools` tests.

While I was at it I standardized on `tempDir` as the variable name for temporary directories, since it was the most common, removing occurrences of `temp` and `tmp`, among others.

Also I factored out some common code that used to catch exceptions that happen on Windows, and made more places use that pattern.

* Try to resolve an intermitted crash during coverage collection

The only theory I can come up with is that maybe the test completes
before we finish processing the standard input, so I made the test
harness wait for the observatory URL before considering whether the
test has finished or not.

Also, some code cleanup while I'm at it, e.g. avoiding using "onFoo"
for the names of methods, avoiding back-to-back switch statements with
the same values, avoiding `_` argument names, and using `?.` instead
of `if (foo != null) foo.`.

* Revert back the signature of _pipeStandardStreamsToConsole

* Also remove the other additions to this method.

* Add '-t' option to 'attach' command.

* Add test

* Make analyzer happy

* Fix tests so they use memory file system and can find lib/main.dart

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