Revert of Use CopyOnWriteBuffer instead of Buffer to avoid unnecessary copies.

webrtc/api/objc/RTCDataChannel.mm

Index: webrtc/api/objc/RTCDataChannel.mm
diff --git a/webrtc/api/objc/RTCDataChannel.mm b/webrtc/api/objc/RTCDataChannel.mm
index 98599058ee8ebec28ba52f096ad3a816c56b8034..5778cb5b7afd19602c754c6467268cbd0c6c06a2 100644
--- a/webrtc/api/objc/RTCDataChannel.mm
+++ b/webrtc/api/objc/RTCDataChannel.mm
@@ -53,8 +53,8 @@
 - (instancetype)initWithData:(NSData *)data isBinary:(BOOL)isBinary {
   NSParameterAssert(data);
   if (self = [super init]) {
-    rtc::CopyOnWriteBuffer buffer(
-        reinterpret_cast<const uint8_t*>(data.bytes), data.length);
+    rtc::Buffer buffer(reinterpret_cast<const uint8_t*>(data.bytes),
+                       data.length);
     _dataBuffer.reset(new webrtc::DataBuffer(buffer, isBinary));
   }
   return self;