Add iOS tracing.

webrtc/base/objc/RTCTracing.mm

Index: webrtc/base/objc/RTCTracing.mm
diff --git a/webrtc/base/objc/RTCTracing.mm b/webrtc/base/objc/RTCTracing.mm
new file mode 100644
index 0000000000000000000000000000000000000000..a51c7033402df2e8e822fb053d9265fac5a38b50
--- /dev/null
+++ b/webrtc/base/objc/RTCTracing.mm
@@ -0,0 +1,29 @@
+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#import "webrtc/base/objc/RTCTracing.h"
+
+#include "webrtc/base/event_tracer.h"
+
+void RTCSetupInternalTracer() {
+  rtc::tracing::SetupInternalTracer();
+}
+
+BOOL RTCStartInternalCapture(NSString *filePath) {
+  return rtc::tracing::StartInternalCapture(filePath.UTF8String);
+}
+
+void RTCStopInternalCapture() {
+  rtc::tracing::StopInternalCapture();
+}
+
+void RTCShutdownInternalTracer() {
+  rtc::tracing::ShutdownInternalTracer();
+}