Ensures we don't regress https://github.com/flutter/flutter/issues/6577.

* More restricted versioning on iOS

* Escape the key base64 and don't echo it back on travis

* Have match not print back the cert url

* Keep the intermediate APK signed the same way before going to the play store

* Don't run on PRs

* iOS works

* Works on Android

* Take in commit number in iOS also. Get rid of image upload for Android. It's just a waste of bandwidth

* Tweak to fix on Travis

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

* review comments

https://github.com/flutter/flutter/issues/10940

This reverts commit b800654a.

This time, do so in Travis' sudo-enabled environment,
which is said to be less prone to networking issues.
It also means we'll run in an env with 7.5GB of RAM
instead of 4GB or RAM (at the cost of about 45 seconds
of extra boot-up time).

https://github.com/flutter/flutter/issues/10940

This reverts commit aa904a58.

Fixes #10940

https://github.com/flutter/flutter/issues/10940

Uploading the coverage data file to Google Storage will make it easier
for folks to get current coverage data quickly.

This moves all the bot-related files to `dev/bots`, hiding it from our
home page in github. Also, simplifies the travis setup, though that
doesn't do any difference to the performance sadly.

* avoid sending analytics on ci systems

* review comments

* add google analytics

* send in the run target type

* track device type targets

* use the real GA code

* review comments

* rev to usage 2.0

* rev to 2.2.0 of usage; add tests

* review comments

We don't need this anymore.

Now that we don't require the Dart SDK to be in your path, it's hard to run
./dev/update_packages.dart. Instead, you can now run `flutter update-packages`.

Fixes #1906

Downloading these packages from cloud storage simplifies our deployment
story because we can upload to cloud storage automatically from the
buildbot.

This patch also switches the responsibility for downloading the engine
artifacts to update_engine.sh. Centralizing this responsibility ensures
that the packages and the binaries are always in sync.

The patch teaches Travis how to update our API docs continuously as we land
patches in master.

Now you can run tests with and without --flutter-repo with a prebuilt binary on
Linux.

Fixes #307

Turns out that ignoring all error lines that match the empty string is a
poor way to go.

Also, we have to update all the example packages now too, since we
analyze them. So just have travis use our update script.

Also, remove flutter_tools' old travis stuff. It's now part of a bigger
repo.

Also, make travis use the dev Dart SDK, since we need the new analyzer.
Stable is way too out of date, e.g. it still complains about libraries
not having names and mixins using 'super', and the strong mode hints are
even more aggressive than on dev.

Rather than using the Flutter unit tests to test FLX, we can just test FLX
directly. Also, clean up the dependencies in the pubspec to match the code.