Update API for Objective-C RTCStats.

webrtc/api/objc/RTCStats.mm

+/*
+ *  Copyright 2015 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 "RTCStats.h"
+
+#import "webrtc/api/objc/RTCStats+Private.h"
+#import "webrtc/base/objc/NSString+StdString.h"
+
+@implementation RTCStats
+
+@synthesize timestamp = _timestamp;
+@synthesize type = _type;
+@synthesize id = _id;
+@synthesize values = _values;
+
+- (NSString *)description {
+  return [NSString stringWithFormat:@"RTCStats:\n%@\n%@\n%f\n%@",
+                                    _id,
+                                    _type,
+                                    _timestamp,
+                                    _values];
+}
+
+#pragma mark - Private
+
+- (instancetype)initWithStatsReport:(const webrtc::StatsReport &)stats {
+  if (self = [super init]) {
+    _timestamp = stats.timestamp();
+    _type = [NSString stringForStdString:stats.TypeToString()];
+    _id = [NSString stringForStdString:stats.id()->ToString()];
+
+    NSMutableDictionary *values =
+        [NSMutableDictionary dictionaryWithCapacity:stats.values().size()];
+    for (auto const &valuePair : stats.values()) {
+        NSString *key = [NSString stringForStdString:
+            valuePair.second->display_name()];
+        NSString *value = [NSString stringForStdString:
+            valuePair.second->ToString()];
+        values[key] = value;

[tkchin_webrtc, 2016/01/05 20:08:17]

Per other CR, there may be a problem here with repeated keys.
Add a warning to log if that happens.

[hjon, 2016/01/06 00:39:14]

Done.

+    }
+    _values = [NSDictionary dictionaryWithDictionary:values];
+  }
+  return self;
+}
+
+@end