* Request the user upgrade if the Android SDK version is 24

* Update android_sdk_test.dart

* Update android_sdk.dart

This matches the default for Runner.xcodeproj and fixes a linker warning
when the two projects use different values.

Add 20x20 notification icons.
Remove unused 76x76 (3x scale) icon.
Fixes warnings for missing/unused icon assets in Xcode 8.2.x

This prevents project re-validation on initial Xcode launch.

1. Add matchers for the `ProcessExit` exception class
2. Add ability to control the setup of the `AppContext` we use in
   `testUsingContext()`
3. Clean up the code that figures out the location of `Cache.flutterRoot`
   such that it works with `pub run test`. It previously only worked
   when the tests were invoked with standalone `dart`

`#3` above will also help unblock #7941

* Small update to instructional comments in app template

* Update Flutter Driver comment

Good suggestion to add the link, Seth! I also updated the working to match what that page uses.

Engine roll to include https://github.com/flutter/engine/pull/3462

* clamp the pixels used in the page calculation to be within min + max extents to avoid pages outside of the range of children

* add test to check onPageChanged not fired on overscroll

Fix a few regressions.

Covers lib/ in package:flutter.

* add crash reporting without enabling it

* do not drop futures on the floor

* return exitCode from executable run

* debug travis

* remove unnecessary todo

* rename local fs getter

Fixes #8557

* Use exact Ahem and exact dimensions for test

* use ‘px’ everywhere

This feature lets you see a portion of the next and previous page in a
PageView.

Fixes #8408

Previously, we would create a simulation whose initial velocity did not match
the requested parameters. We now compute the parameters for the simulation in a
way that ensures all the math works out.

Fixes #8255

* fix FLUTTER_ANSI_TERMINAL check

should have been included in the previous PR :(

* review comments