Update CONTRIBUTING.md to add iOS engine development instructions. (#2844)
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 77f1e28..82a86ed 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -112,9 +112,21 @@
`android/AndroidManifest.xml` file for the Flutter app you are using
to test the engine.
-### iOS
+### iOS (cross-compiling from Mac)
-See [this wiki page](https://github.com/flutter/engine/wiki/Flutter-Apps-on-iOS).
+* Make sure you have Xcode 7.3.0+ installed.
+* `gclient sync` to update dependencies.
+* `./sky/tools/gn --ios --unoptimized` to prepare build files.
+ * For a discussion on the various flags and modes, [read this discussion](https://github.com/flutter/flutter/wiki/Flutter's-modes).
+* `ninja -C out/ios_debug_unopt` to build iOS artifacts.
+
+Once the artifacts are built, you can start using them in your application by following these steps:
+* `cd /path/to/flutter/examples/hello_world`
+* `pub get`
+* `../../bin/flutter run --local-engine-src-path /path/to/engine/src --local-engine=ios_debug_unopt`
+ * Depending on the configuration you built, modify the `local-engine` flag.
+* If you are debugging crashes in the engine, you can connect the `LLDB` debugger from `Xcode` by opening `ios/Runner.xcodeproj` and starting the application by clicking the Run button (CMD + R).
+
### Desktop (Mac and Linux), for tests
