Currently only android-arm and ios are supported target platforms.

On iOS, we use Xcode to build a static library that contains the precompiled
code. This code is currently unused, but it will be used by the new Xcode
harness to factor out as much complexity as possible into the flutter tool.

Our microbenchmarks now run on real devices.

Wire up ios-profile and ios-release. Switching between debug, profile and release starts the build process from scratch. (#4063)

We now match the spec much better, including handling dark theme.

The main thing we're still missing is the landscape layout.

Fixes #989

Fixes the breakage that https://github.com/flutter/flutter/pull/4092 would cause.

Small fixes to contributing documentation.

 - Using widgets/spinning_square.dart instead of non-existing
  examples/widgets for the `run -t` example
 - travis/test.sh -> dev/bots/test.sh
 - Couple of style changes.

For developers with the platform tools installed but no SDK, it prevents
crashing in the flutter tool in favor of more user-friendly error messages
downstream.

* New Material Design calculator example. (Attempt 2 after git fetch upstream).

* Responded to code review.

* Second round of code review.

Rev the dart sdk to 1.17.0-dev.4.1

Keeps up with the Joneses, pulling in the latest dev build (and with it a number of stability and perf improvements).

Looks like our intent here was to show the tab label rather than
"Instance of '_Page'".

Also, fix an issue where the scrollableKey wasn't being forwarded to the
actual scrollable.

Fixes #3090

Fix analyzer field overrides.

Cleans up 3 of the 4 violations of the `overriden_field` lint.

The last one is more interesting and I'll defer to someone closer to that code:

    [lint] Do not override fields. (packages/flutter/test/rendering/rendering_tester.dart, line 91, col 14)

@chinmaygarde