This should make the message in Travis logs look better.

Xcode builds depend on the Python 'six' module. If not present, exit
immediately with a useful error message.

The six module is included in the system default Python installation. We
perform this check in case a custom Python install has higher priority
on $PATH; e.g., due to a Homebrew or MacPorts installation.

This extracts an existing doctor check to use it during the build step
as well.

This reverts commit 8f9d4a22.

* add @required when there's an assert not null

* address review comments

Related #8876

Plugin projects are created by running `flutter create --plugin <name>`.

An example app is also created in the plugin project, using the normal 'create' template, which has been modified to allow for conditional plugin code.

Modified the android package name to match package naming conventions (all lower-case, and must match the directory name).

Fixes #7307

This reverts commit e2b49d64.

* enable crash reporting in flutter_tools

* fix analytics text; use relative paths

* fix test

* Bump to Dart SDK 1.23.0-dev.10

* allows us to understand flutter usage via telemetry
* brings in `@immutable`

Fixes: #9042

* completer fix

* Update to platform 1.1.1.

Revert "Revert "Revert "Include fragment support in Android build to allow use of FragmentActivity in FlutterActivity (#9036)"" (#9046)" (#9047)

Test is still failing with increased timeout.

This reverts commit 864b3c37.

Revert "Revert "Include fragment support in Android build to allow use of FragmentActivity in FlutterActivity (#9036)"" (#9046)

Increased the time limit slightly to allow the microbenchmark test time to finish.

Revert "Include fragment support in Android build to allow use of FragmentActivity in FlutterActivity (#9036)" (#9041)

This reverts commit 6bf0ceb0.

Include fragment support in Android build to allow use of FragmentActivity in FlutterActivity (#9036)

The very first time `pod install` is invoked, CocoaPods downloads the master spec repository, which takes quite a while. Before this change, the build appeared to have stalled. With this change, at least the spinner is moving.

Added `pod setup` to the install instructions for CocoaPods, so the spec repo is downloaded while setting up Flutter, instead of during the first build.

Old Android Stuio versions pior to 2.2.0 didn't come with Java bundled. Make sure flutter doesn't crash when we try to determine the Java version of those old Android Studio installations.

* Use Java bundled with Android Studio for gradle

* review comments

Go through all packages brought in by pub, and write the name and path of every one that is a flutter plugin into .flutter-plugins.

In android/settings.gradle and ios/Podfile, read in .flutter-plugins, if that file exists. The Android / iOS code from the plugins is automatically added as dependencies of the native code of the app.

**THIS IS A BREAKING CHANGE.** See below for migration steps for
existing projects.

Previously, Flutter app code was built as a raw dylib on iOS.  Dynamic
libraries outside of a framework bundle are not supported on iOS, except
for the system Swift libraries provided by Xcode.

See:
https://developer.apple.com/library/content/technotes/tn2435/_index.html#//apple_ref/doc/uid/DTS40017543-CH1-TROUBLESHOOTING_BUNDLE_ERRORS-EMBEDDED__DYLIB_FILES

* Migrates Xcode build from app.dylib to App.framework
* Migrates flutter create template
* Migrates example projects

Migration steps for existing projects
=====================================

The following steps should be taken from the root of your Flutter
project:

1. Edit `ios/.gitignore`: add `/Flutter/App.framework` on a new line.
2. In the Xcode project navigator, remove `app.dylib` from the Flutter
   folder. Delete this file from the `ios/Flutter` directory in your project.
3. Run a build to generate `ios/Flutter/App.framework`. From the command
   line, run `flutter build ios`. If you have not configured app signing
   in Xcode, an alternative method is to open the simulator, then run
   `flutter run -d iP`.
4. In the Xcode project navigator, select the `Runner` project. In the
   project settings that are displayed in the main view, ensure that the
   `Runner` target is selected. You can verify this by exposing the
   sidebar using the [| ] icon in the upper-left corner of the main
   view.
5. Select the *General* tab in the project settings. Under the
   *Embedded Binaries* section, click '+' to add `App.framework`. In the
   sheet that drops down, click the *Add Other...* button. Navigate to
   the `ios/Flutter` directory and select `App.framework`. Click *Open*.
   In the sheet that drops down, select *Create folder references*, then
   click *Finish*.
6. In the project settings, verify that `App.framework` has been added to the
   *Embedded Binaries* and *Linked Frameworks and Libraries* lists.
7. In the Xcode project navigator, drag `App.framework` under the
   Flutter folder.
8. In the Xcode project navigator, select `Flutter` then from the
   *File* menu, select *Add Files to "Runner"...*. Navigate to the
   `ios/Flutter` directory, select `AppFrameworkInfo.plist` and click
   the *Add* button.
9. From the command line, in your project directory, run
   `flutter build clean`, then `flutter run`.

At this point your project should be fully migrated.

* Teach flutter_tools to populate PUB_ENVIRONMENT

Will allow telemetry reporting on pub.dartlang.org once
flutter moves to 1.23.0-dev.10.0

* review changes

* Print error message if a package is skipped during DevFS sync.

* review comments

* more review comments

* fix test