* Adds a PageRouteObserver

Required for https://github.com/flutter/plugins/pull/174.
See also https://github.com/flutter/flutter/issues/11216.

* formatting fixes

* Make RouteObserver generic

Fixes https://github.com/flutter/flutter/issues/10917

* Quiet debug test runner output when in machine mode.

See: https://github.com/flutter/flutter-intellij/issues/1176

* json => machine

flutter_tools depends on cli_util, plugin, and stream_channel but hadn't
explicitly declared them as dependencies.

In some cases, we've seen interactions between Instruments and the iOS
simulator that cause hung instruments and DTServiceHub processes. If
enough instances pile up, the host machine eventually becomes
unresponsive.

Until the underlying issue is resolved, manually kill any orphaned
instances (where the parent process has died and PPID is 1) before
launching another instruments run.

It's probably too much of a foot gun.

Also, emphasize what you have to do in case people didn't read the design principles document.

* fix examples/layers/widgets/gestures.dart

* use a list of colors to avoid error prone in elseif

* address review comments

* add tests

* keep index to lower complexity

* address review comments

* Disable cocoapods stats

* Add a comment for code readers

* fix new test

* start

* with create

* refactor cocoapod code, add tests

* fix tests

* throw when cocoapod missing

* obj-c projects don’t use use_framework!

Apply a 30 second timeout to Android/iOS device polling.

If there's a device poll already in progress, skip polling for new
devices; wait for the first request to return/timeout.

Was broken by https://github.com/flutter/flutter/commit/dba29aa0fce684b201c6b03efc73ba607c7b507b, which apprently has been pushed directly to master without running through Travis?

Fixes #9413.

For more info on conditional imports, see
https://github.com/munificent/dep-interface-libraries/blob/master/Proposal.md.

Github makes own copies of images referenced in README, and that fails for large image sizes. The gif has 6MB and so is over the threshold.

Instead of using an off-GitHub image, use the same image uploaded to user-images.githubusercontent.com. This makes GitHub show the image even when it's very large.

This reverses https://github.com/flutter/flutter/pull/11170 and finalizes https://github.com/flutter/flutter/pull/11158.

Github makes copies of images referenced in README, and it fails for large image sizes. The gif has 6MB and so is over the threshold.

This removes the image until I can figure out how to reinsert it so that it shows.

Reuses flutter.io homepage content to give README.md an upgrade, since this file will be the shop window of Flutter to a large part of newcomers. 

The downside is that we now have duplicate content that should be updated in unison with the main site but which cannot be easily copy-pasted, due to constraints of github's Markdown renderer.

* requires bumping `process` to a version that has
  relaxed version restrictions on `intl`

https://github.com/flutter/flutter/issues/10650

* Don't pollute Travis log with Google Cloud SDK installation

* review comments

* a11y fix for list_demo.dart

* fix semantics of persistant bottom sheet

* add Android instrumentation test

* add devicelab test

* add to manifest.yaml

* rename _smoke_test.dart to _smoketest.dart to prevent flutter test from picking it up

* volatile fields; style fixes

* use ConditionVariable; fix sh script

Fixes #7894

The output of the analyzer gives the full path to the Dart file, so
we had to adjust the string matching to account for that.

https://github.com/flutter/flutter/issues/7894

* Include the process' `stdout` and `stderr` when it returns a
  non-zero exit code in `runCheckedAsync()`
* Defensively catch errors in `AndroidDevice.isAppInstalled()`
  and return false