Let receiving() and SignalRecevingState be part of rtc::PacketTransportInterface.

Writable() and the related signal are already part of rtc::PacketTransportInterface. Sense of code symmetry aesthetics dictates that receiving() and the related signal should be declared in the same place.

BUG=webrtc:6531

Review-Url: https://codereview.webrtc.org/2444793003
Cr-Commit-Position: refs/heads/master@{#14865}

webrtc/p2p/base/dtlstransportchannel.cc

@@ -471,9 +471,10 @@ void DtlsTransportChannelWrapper::OnWritableState(
   }
 }
 
-void DtlsTransportChannelWrapper::OnReceivingState(TransportChannel* channel) {
+void DtlsTransportChannelWrapper::OnReceivingState(
+    rtc::PacketTransportInterface* transport) {
   ASSERT(rtc::Thread::Current() == network_thread_);
-  RTC_DCHECK(channel == channel_);
+  RTC_DCHECK(transport == channel_);
   LOG_J(LS_VERBOSE, this)
       << "DTLSTransportChannelWrapper: channel receiving state changed to "
       << channel_->receiving();

webrtc/p2p/base/dtlstransportchannel.h

@@ -216,7 +216,7 @@ class DtlsTransportChannelWrapper : public TransportChannelImpl {
   void OnSentPacket(rtc::PacketTransportInterface* transport,
                     const rtc::SentPacket& sent_packet);
   void OnReadyToSend(rtc::PacketTransportInterface* transport);
-  void OnReceivingState(TransportChannel* channel);
+  void OnReceivingState(rtc::PacketTransportInterface* transport);
   void OnDtlsEvent(rtc::StreamInterface* stream_, int sig, int err);
   bool SetupDtls();
   void MaybeStartDtls();

webrtc/p2p/base/packettransportinterface.h

@@ -36,6 +36,10 @@ class PacketTransportInterface : public sigslot::has_slots<> {
   // The transport has been established.
   virtual bool writable() const = 0;
 
+  // The transport has received a packet in the last X milliseconds, here X is
+  // configured by each implementation.
+  virtual bool receiving() const = 0;
+
   // Attempts to send the given packet.
   // The return value is < 0 on failure. The return value in failure case is not
   // descriptive. Depending on failure cause and implementation details
@@ -70,6 +74,9 @@ class PacketTransportInterface : public sigslot::has_slots<> {
   //  SendPacket's return code and/or GetError.
   sigslot::signal1<PacketTransportInterface*> SignalReadyToSend;
 
+  // Emitted when receiving state changes to true.
+  sigslot::signal1<PacketTransportInterface*> SignalReceivingState;
+
   // Signalled each time a packet is received on this channel.
   sigslot::signal5<PacketTransportInterface*,
                    const char*,

webrtc/p2p/base/transportchannel.h

@@ -76,9 +76,8 @@ class TransportChannel : public rtc::PacketTransportInterface {
   // Returns the states of this channel.  Each time one of these states changes,
   // a signal is raised.  These states are aggregated by the TransportManager.
   bool writable() const override { return writable_; }
-  bool receiving() const { return receiving_; }
+  bool receiving() const override { return receiving_; }
   DtlsTransportState dtls_state() const { return dtls_state_; }
-  sigslot::signal1<TransportChannel*> SignalReceivingState;
   // Emitted whenever DTLS-SRTP is setup which will require setting up a new
   // SRTP context.
   sigslot::signal2<TransportChannel*, DtlsTransportState> SignalDtlsState;

webrtc/p2p/base/transportcontroller.cc

@@ -573,7 +573,8 @@ void TransportController::OnChannelWritableState_n(
   UpdateAggregateStates_n();
 }
 
-void TransportController::OnChannelReceivingState_n(TransportChannel* channel) {
+void TransportController::OnChannelReceivingState_n(
+    rtc::PacketTransportInterface* transport) {
   RTC_DCHECK(network_thread_->IsCurrent());
   UpdateAggregateStates_n();
 }

webrtc/p2p/base/transportcontroller.h

@@ -206,7 +206,7 @@ class TransportController : public sigslot::has_slots<>,
 
   // Handlers for signals from Transport.
   void OnChannelWritableState_n(rtc::PacketTransportInterface* transport);
-  void OnChannelReceivingState_n(TransportChannel* channel);
+  void OnChannelReceivingState_n(rtc::PacketTransportInterface* transport);
   void OnChannelGatheringState_n(TransportChannelImpl* channel);
   void OnChannelCandidateGathered_n(TransportChannelImpl* channel,
                                     const Candidate& candidate);