Move Flutter Gallery to dev/integration_tests/ as it is an older copy used only for testing. The current version of the Flutter Gallery now lives in https://github.com/flutter/gallery.

While building the iOS platform views support we only enabled it when the app developer explicitly specified it with a flag, the main reasons were using an untested thread configuration, and taking a performance hit (even when no platform view is used due to disabled raster cache).

Now that we are using the same dynamic thread configuration whether platform views is used or not, and that raster cache works with platform views in the tree as well, we are almost ready to enabled the platform views support by default.

As a first step, I'm enabling it for the Flutter Gallery app on which we run benchmarks. After monitoring the benchmarks and making sure the gallery takes no hit we should be more confident to enabled platform views by default.

This change is expected to have no performance effect on the Gallery app at all.

Change Xcode project developmentRegion to 'en' and plist CFBundleDevelopmentRegion to DEVELOPMENT_LANGUAGE (#34293)

This results in running Flutter Gallery with one less thread (platform
and gpu threads are the the same).

This is very likely to cause a regression in the iOS Gallery benchmarks.
I'm mainly interested in landing this to see how much the benchmarks
regress, and it's likely that we will revert it shortly after landing.

Build universal armv7+arm64 binary for iOS now that our tooling supports
it.

Already enabled on Android.

As of Xcode 7, Apple recommends setting the bundle identifier in the
PRODUCT_BUNDLE_IDENTIFIER build variable and setting CFBundleIdentifier
to that variable in Info.plist.

As of Xcode 8, CLANG_WARN_INFINITE_RECURSION and CLANG_WARN_SUSPICIOUS_MOVE
are recommended settings.

We now use a different approach for ios projects where the developer controls
the Xcode project file. This patch removes the old ".generated" approach in
favor of the new approach.

Initial version of complex layout performance test