appveyor.com runs our tests on Windows for each PR.

Only implemented for Android devices for now. Compare the installed SHA1
to the latest build. If they match, there's no reason to reinstall the
build.

Fixes #8295

* Fix bug parsing Gradle version.

Version from pub_semver requires versions of the format X.Y.Z. Gradle
doesn't follow semantic versioning, though, so version parsing would
fail on versions like '3.2'. Fixed by writing a custom Version class.

Also removed a check for apksigner when building Gradle-based projects.

Fixes #8298

Previously, a ListView would always accept user input, even if it wasn't
actually scrollable. Now, by default, we don't accept user input if there's no
scroll range. You can override this behavior using the ScrollPhysics.

Fixes #8276
Fixes #8278
Fixes #8271

This reverts commit 70d7fe3a.

The Java version missmatch on the bots has been resolved.

Otherwise tapping the menu button causes the bottom sheet to disappear and
reappear.

Fixes #8275

This enables us to run more tests on Windows.

This functionality is independently useful.

Fixes #8293

Discuss how to change paint order.

It doesn't need to be in the same file as RenderSliver.

Do not attempt to deploy/debug wifi connected iOS devices. ios-deploy is
able to install over wifi, but we've had several bugs reporting failure
to run/debug once installation has completed when the device is also
connected via USB. Note that we don't currently support deploy/debug
over wifi since libimobiledevice (which is also required) requires a USB
connection.

This functionality got lots somehow in the migration to maybePop.

Fixes #8258

Previously we called onPageChanged when the scroll ended, but that is too late.
Now we call onPageChanged when we cross the halfway mark, which, for example,
makes the tab indicator update earlier.

Fixes #8265

Works around https://github.com/dart-lang/test/issues/545

Fixes #7734

* Remove SHA1 check from AndroidDevice.isAppInstalled()

The docs for isAppInstalled say 'check if a version of the given app is
already installed', however the current code returns true only if it's
the latest build that's installed.

This made sense in the past, when the use pattern was:

  if (!isAppInstalled(...)) installApp(...);

but now the usage is:

  if (isAppInstalled(...)) uninstallApp(...);
  installApp(...);

This has the probably unintended consequence that if you run `flutter
install` or `flutter run` two times in a row with no source changes, the
second invocation will uninstall the app, but the first invocation might
not.

Removing the SHA1 check makes us always uninstall the app if it's
installed.

Fixes #8172

Finally found the command to run tests in checked mode on my system. This one should've been caught by the IDE, but wasn't.

* Teach flutter tools to find gradle

Flutter tools will now use Gradle from Android Studio, which is now found automatically.

flutter doctor will verify that Android Studio has been installed, and that the included Gradle is at least version 2.14.1.

It is still possible to manually configure the path to Android Studio (flutter config --android-studio-dir=XXX) or Gradle (flutter config --gradle-dir=XXX), but this should only be necessary if they're installed somewhere non-standard.

Only tested on Linux and macOS for now.

Fixes #8131

When resizing a PageView from 0x0, we weren't sure what the old page
number was because all the pages are collapsed at zero. Now we avoid the
divide by zero and default to the initialPage.

Fixes #8285

Previously, we were dividing by zero.

Fixes #8281

Also, make all painters have a toString by default.

Now that all the breaking scrolling changes are in, this seems like a reasonble
time to rev package:flutter's version number.

Rename all the "2" classes related to scrolling to remove the "2". Now that the
old scrolling code is gone, we don't need to use the suffix.

* Do not attempt to merge non-fat frameworks in Xcode build

During the Xcode build, we strip code irrelevant to the target
architecture in frameworks used by the application. In the case of
non-fat executables, no stripping occurs, so the frameworks can be used
as-is. No merge & replace step is necessary.

* fixup! Do not attempt to merge non-fat frameworks in Xcode build

* More better toStrings and more vigorous smoke testing of gallery

* Update scroll_controller.dart

* Update sliver.dart

* Add --start-paused doc

* correcting > Observatory

* Updating --start-paused option w/feedback

Artifacts are now located in a central place.
This will enable us to downlaod artifacts when we need them (instead of
downloading them all upfront).
This also makes replacing sky_snapshot with gen_snapshot easier.