Add stats overlay to iOS AppRTCDemo.

webrtc/examples/objc/AppRTCDemo/common/ARDUtilities.m

Index: webrtc/examples/objc/AppRTCDemo/common/ARDUtilities.m
diff --git a/webrtc/examples/objc/AppRTCDemo/common/ARDUtilities.m b/webrtc/examples/objc/AppRTCDemo/common/ARDUtilities.m
index 257b6a6a5c9e6ed6d61b5654990ac50a1a269b92..6b5358c66f4202e21e4481a9d11d51df7c8c4736 100644
--- a/webrtc/examples/objc/AppRTCDemo/common/ARDUtilities.m
+++ b/webrtc/examples/objc/AppRTCDemo/common/ARDUtilities.m
@@ -10,6 +10,8 @@
 
 #import "ARDUtilities.h"
 
+#import <mach/mach.h>
+
 #import "RTCLogging.h"
 
 @implementation NSDictionary (ARDUtilites)
@@ -93,3 +95,34 @@
 }
 
 @end
+
+NSInteger ARDGetCpuUsagePercentage() {
+  // Create an array of thread ports for the current task

[jiayl2, 2015/08/13 22:21:50]

nit: '.' at the end of a comment. here and other places.

[tkchin_webrtc, 2015/08/13 23:55:31]

Done.

+  const task_t task = mach_task_self();
+  thread_act_array_t thread_array;
+  mach_msg_type_number_t thread_count;
+  if (task_threads(task, &thread_array, &thread_count) != KERN_SUCCESS) {
+    return -1;
+  }
+
+  // Sum cpu usage from all threads
+  float cpu_usage_percentage = 0;
+  thread_basic_info_data_t thread_info_data = {};
+  mach_msg_type_number_t thread_info_count;
+  for (size_t i = 0; i < thread_count; ++i) {
+    thread_info_count = THREAD_BASIC_INFO_COUNT;
+    kern_return_t ret = thread_info(thread_array[i],
+                                    THREAD_BASIC_INFO,
+                                    (thread_info_t)&thread_info_data,
+                                    &thread_info_count);
+    if (ret == KERN_SUCCESS) {
+      cpu_usage_percentage +=
+          100.f * (float)thread_info_data.cpu_usage / TH_USAGE_SCALE;
+    }
+  }
+
+  // Dealloc the created array
+  vm_deallocate(task, (vm_address_t)thread_array,
+                sizeof(thread_act_t) * thread_count);
+  return lroundf(cpu_usage_percentage);
+}