Add ObjC API for getting native histograms.

webrtc/sdk/objc/Framework/Classes/RTCMetric+Private.h

Index: webrtc/sdk/objc/Framework/Classes/RTCMetric+Private.h
diff --git a/webrtc/build/ios/SDK/PodTest/PodTest/AppDelegate.h b/webrtc/sdk/objc/Framework/Classes/RTCMetric+Private.h
similarity index 57%
copy from webrtc/build/ios/SDK/PodTest/PodTest/AppDelegate.h
copy to webrtc/sdk/objc/Framework/Classes/RTCMetric+Private.h
index de2cc0465db198c0462876e2391651948837cca4..6ae2ec0fa8e7328d482fbd281f0011ea166e789a 100644
--- a/webrtc/build/ios/SDK/PodTest/PodTest/AppDelegate.h
+++ b/webrtc/sdk/objc/Framework/Classes/RTCMetric+Private.h
@@ -8,10 +8,18 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#import <UIKit/UIKit.h>
+#import "WebRTC/RTCMetric.h"
 
-@interface AppDelegate : UIResponder <UIApplicationDelegate>
+#include "webrtc/system_wrappers/include/metrics_default.h"
 
-@property (strong, nonatomic) UIWindow *window;
+NS_ASSUME_NONNULL_BEGIN
+
+@interface RTCMetric ()
+
+/** Initialize an RTCMetric object from native SampleInfo. */
+- (instancetype)initWithNativeSampleInfo:
+    (const webrtc::metrics::SampleInfo&)info;
 
 @end
+
+NS_ASSUME_NONNULL_END