Add ObjC API for getting native histograms.

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMetrics.h

Index: webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMetrics.h
diff --git a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCSSLAdapter.h b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMetrics.h
similarity index 59%
copy from webrtc/sdk/objc/Framework/Headers/WebRTC/RTCSSLAdapter.h
copy to webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMetrics.h
index 1341a5c003cda97b8909c4f272915250ce3039fc..4a0d678f59240cb3fc099611a5c86984efb345d6 100644
--- a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCSSLAdapter.h
+++ b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMetrics.h
@@ -11,10 +11,13 @@
 #import <Foundation/Foundation.h>
 
 #import <WebRTC/RTCMacros.h>
+#import <WebRTC/RTCMetricsSampleInfo.h>
 
 /**
- * Initialize and clean up the SSL library. Failure is fatal. These call the
- * corresponding functions in webrtc/base/ssladapter.h.
+ * Enables gathering of metrics (which can be fetched with
+ * RTCGetAndResetMetrics). Must be called before any other call into WebRTC.
  */
-RTC_EXTERN BOOL RTCInitializeSSL();
-RTC_EXTERN BOOL RTCCleanupSSL();
+RTC_EXTERN void RTCEnableMetrics();
+
+/** Gets and clears native histograms. */
+RTC_EXTERN NSArray<RTCMetricsSampleInfo*>* RTCGetAndResetMetrics();