Add macros to mark APIs as being deprecated or unavailable. (flutter#…

…4401)

shell/platform/darwin/ios/framework/Headers/Flutter.h

@@ -5,6 +5,12 @@
 #ifndef FLUTTER_FLUTTER_H_
 #define FLUTTER_FLUTTER_H_
 
+/**
+ BREAKING CHANGES:
+
+ November 29, 2017: Added a BREAKING CHANGES section.
+ */
+
 #include "FlutterAppDelegate.h"
 #include "FlutterBinaryMessenger.h"
 #include "FlutterChannels.h"

shell/platform/darwin/ios/framework/Headers/FlutterMacros.h

@@ -20,4 +20,21 @@
 #define NS_ASSUME_NONNULL_END _Pragma("clang assume_nonnull end")
 #endif  // defined(NS_ASSUME_NONNULL_BEGIN)
 
+/**
+ Indicates that the API has been deprecated for the specifed reason. Code that
+ uses the deprecated API will continue to work as before. However, the API will
+ soon become unavailable and users are encouraged to immediately take the
+ appropriate action mentioned in the deprecation message and the BREAKING
+ CHANGES section present in the Flutter.h umbrella header.
+ */
+#define FLUTTER_DEPRECATED(msg) __attribute__((__deprecated__(msg)))
+
+/**
+ Indicates that the previously deprecated API is now unavailable. Code that
+ uses the API will not work and the declaration of the API is only a stub meant
+ to display the given message detailing the actions for the user to take
+ immediately.
+ */
+#define FLUTTER_UNAVAILABLE(msg) __attribute__((__unavailable__(msg)))
+
 #endif  // FLUTTER_FLUTTERMACROS_H_