Enable iOS AppRTCDemo send side BWE.

webrtc/base/objc/RTCFieldTrials.h

Index: webrtc/base/objc/RTCFieldTrials.h
diff --git a/webrtc/base/objc/RTCTracing.h b/webrtc/base/objc/RTCFieldTrials.h
similarity index 53%
copy from webrtc/base/objc/RTCTracing.h
copy to webrtc/base/objc/RTCFieldTrials.h
index 5b8e2f6ac371abe543149a65f54b0d04983ed7cb..13b9ae4d52d99220c26a37658f90f400af74af1c 100644
--- a/webrtc/base/objc/RTCTracing.h
+++ b/webrtc/base/objc/RTCFieldTrials.h
@@ -8,14 +8,14 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#import <Foundation/Foundation.h>
+#include "webrtc/base/objc/RTCMacros.h"
 
-#import "webrtc/base/objc/RTCMacros.h"
+typedef NS_OPTIONS(NSUInteger, RTCFieldTrialOptions) {
+  RTCFieldTrialOptionsNone = 0,
+  RTCFieldTrialOptionsSendSideBwe = 1 << 0,
+};
 
-RTC_EXPORT void RTCSetupInternalTracer();
-/** Starts capture to specified file. Must be a valid writable path.
- *  Returns YES if capture starts.
+/** Must be called before any other call into WebRTC. See:
+ *  webrtc/system_wrappers/include/field_trial_default.h
  */
-RTC_EXPORT BOOL RTCStartInternalCapture(NSString *filePath);
-RTC_EXPORT void RTCStopInternalCapture();
-RTC_EXPORT void RTCShutdownInternalTracer();
+RTC_EXPORT void RTCInitFieldTrials(RTCFieldTrialOptions options);