MetricKit iOS xcode13.2 b2

#MetricKit.framework https://github.com/xamarin/xamarin-macios/pull/13497

diff -ruN /Applications/Xcode_13.2.0-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/System/Library/Frameworks/MetricKit.framework/Headers/MXAppLaunchMetric.h /Applications/Xcode_13.2.0-beta2.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/System/Library/Frameworks/MetricKit.framework/Headers/MXAppLaunchMetric.h
--- /Applications/Xcode_13.2.0-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/System/Library/Frameworks/MetricKit.framework/Headers/MXAppLaunchMetric.h	2021-10-22 20:32:40.000000000 -0400
+++ /Applications/Xcode_13.2.0-beta2.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/System/Library/Frameworks/MetricKit.framework/Headers/MXAppLaunchMetric.h	2021-11-11 23:14:13.000000000 -0500
@@ -34,6 +34,15 @@
  */
 @property (readonly, strong, nonnull) MXHistogram<NSUnitDuration *> *histogrammedApplicationResumeTime;
 
+/*!
+@property      histogrammedOptimizedTimeToFirstDraw
+@abstract      Histogrammed optimized application time-to-first-draw data.
+@discussion    Dimensioned as NSUnitDuration.
+@discussion    This represents the time when the first CA commit is finished where the application launch has been optimized by the system.
+@discussion    In iOS 15, the system will opportunistically start applications that are not running in the background to reduce the amount of time a user may have to wait before an application is usable. These launches can occur after a system reboot and periodically as system conditions allow.
+*/
+@property (readonly, strong, nonnull) MXHistogram<NSUnitDuration *> *histogrammedOptimizedTimeToFirstDraw API_AVAILABLE(ios(15.2)) API_UNAVAILABLE(macos, tvos, watchos);
+
 @end
 
 NS_ASSUME_NONNULL_END