Initial implementation of onbufferedamountlow

Source/modules/mediastream/RTCDataChannel.cpp

Index: Source/modules/mediastream/RTCDataChannel.cpp
diff --git a/Source/modules/mediastream/RTCDataChannel.cpp b/Source/modules/mediastream/RTCDataChannel.cpp
index d380bcb953df240f7430ebf2ca2712dda7399843..1e756bb8170965b3f9922f955760aded94e3e1cb 100644
--- a/Source/modules/mediastream/RTCDataChannel.cpp
+++ b/Source/modules/mediastream/RTCDataChannel.cpp
@@ -76,6 +76,7 @@ RTCDataChannel::RTCDataChannel(ExecutionContext* context, RTCPeerConnection* con
     , m_binaryType(BinaryTypeArrayBuffer)
     , m_scheduledEventTimer(this, &RTCDataChannel::scheduledEventTimerFired)
     , m_connection(connection)
+    , m_bufferedAmountLowThreshold(0U)
 {
     m_handler->setClient(this);
 }
@@ -156,6 +157,16 @@ unsigned RTCDataChannel::bufferedAmount() const
     return m_handler->bufferedAmount();
 }
 
+unsigned RTCDataChannel::bufferedAmountLowThreshold() const
+{
+    return m_bufferedAmountLowThreshold;
+}
+
+void RTCDataChannel::setBufferedAmountLowThreshold(unsigned threshold)
+{
+    m_bufferedAmountLowThreshold = threshold;
+}
+
 String RTCDataChannel::binaryType() const
 {
     switch (m_binaryType) {
@@ -250,6 +261,14 @@ void RTCDataChannel::didChangeReadyState(WebRTCDataChannelHandlerClient::ReadySt
     }
 }
 
+void RTCDataChannel::didDecreaseBufferedAmount(unsigned previousAmount)
+{
+    if (previousAmount > m_bufferedAmountLowThreshold
+        && bufferedAmount() <= m_bufferedAmountLowThreshold) {
+        scheduleDispatchEvent(Event::create(EventTypeNames::bufferedamountlow));
+    }
+}
+
 void RTCDataChannel::didReceiveStringData(const WebString& text)
 {
     if (m_stopped)