Remove unused SessionId from TransportChannel and PortAllocatorSession.

BUG=

Review-Url: https://codereview.webrtc.org/2237853002
Cr-Commit-Position: refs/heads/master@{#13731}

webrtc/p2p/base/dtlstransportchannel.h

@@ -118,7 +118,6 @@ class DtlsTransportChannelWrapper : public TransportChannelImpl {
   bool GetStats(ConnectionInfos* infos) override {
     return channel_->GetStats(infos);
   }
-  const std::string SessionId() const override { return channel_->SessionId(); }
 
   virtual bool SetSslMaxProtocolVersion(rtc::SSLProtocolVersion version);
 

webrtc/p2p/base/p2ptransportchannel.cc

@@ -447,7 +447,7 @@ void P2PTransportChannel::MaybeStartGathering() {
       }
     } else {
       AddAllocatorSession(allocator_->CreateSession(
-          SessionId(), transport_name(), component(), ice_ufrag_, ice_pwd_));
+          transport_name(), component(), ice_ufrag_, ice_pwd_));
       allocator_sessions_.back()->StartGettingPorts();
     }
   }

webrtc/p2p/base/portallocator.cc

@@ -68,7 +68,6 @@ void PortAllocator::SetConfiguration(
 }
 
 std::unique_ptr<PortAllocatorSession> PortAllocator::CreateSession(
-    const std::string& sid,
     const std::string& content_name,
     int component,
     const std::string& ice_ufrag,

webrtc/p2p/base/portallocator.h

@@ -301,7 +301,6 @@ class PortAllocator : public sigslot::has_slots<> {
   virtual void SetNetworkIgnoreMask(int network_ignore_mask) = 0;
 
   std::unique_ptr<PortAllocatorSession> CreateSession(
-      const std::string& sid,
       const std::string& content_name,
       int component,
       const std::string& ice_ufrag,

webrtc/p2p/base/portallocator_unittest.cc

@@ -15,7 +15,6 @@
 #include "webrtc/p2p/base/fakeportallocator.h"
 #include "webrtc/p2p/base/portallocator.h"
 
-static const char kSessionId[] = "session id";
 static const char kContentName[] = "test content";
 // Based on ICE_UFRAG_LENGTH
 static const char kIceUfrag[] = "UF00";
@@ -39,7 +38,6 @@ class PortAllocatorTest : public testing::Test, public sigslot::has_slots<> {
   }
 
   std::unique_ptr<cricket::FakePortAllocatorSession> CreateSession(
-      const std::string& sid,
       const std::string& content_name,
       int component,
       const std::string& ice_ufrag,
@@ -47,8 +45,7 @@ class PortAllocatorTest : public testing::Test, public sigslot::has_slots<> {
     return std::unique_ptr<cricket::FakePortAllocatorSession>(
         static_cast<cricket::FakePortAllocatorSession*>(
             allocator_
-                ->CreateSession(sid, content_name, component, ice_ufrag,
-                                ice_pwd)
+                ->CreateSession(content_name, component, ice_ufrag, ice_pwd)
                 .release()));
   }
 
@@ -95,7 +92,7 @@ TEST_F(PortAllocatorTest, TestDefaults) {
 // candidate filter are applied as expected.
 TEST_F(PortAllocatorTest, CreateSession) {
   allocator_->set_candidate_filter(cricket::CF_RELAY);
-  auto session = CreateSession(kSessionId, kContentName, 1, kIceUfrag, kIcePwd);
+  auto session = CreateSession(kContentName, 1, kIceUfrag, kIcePwd);
   ASSERT_NE(nullptr, session);
   EXPECT_EQ(cricket::CF_RELAY, session->candidate_filter());
   EXPECT_EQ(kContentName, session->content_name());

webrtc/p2p/base/transportchannel.h

@@ -66,10 +66,6 @@ class TransportChannel : public sigslot::has_slots<> {
     return TransportChannelState::STATE_CONNECTING;
   }
 
-  // TODO(mallinath) - Remove this API, as it's no longer useful.
-  // Returns the session id of this channel.
-  virtual const std::string SessionId() const { return std::string(); }
-
   const std::string& transport_name() const { return transport_name_; }
   int component() const { return component_; }
 

webrtc/p2p/client/basicportallocator_unittest.cc

@@ -235,8 +235,8 @@ class BasicPortAllocatorTest : public testing::Test,
       int component,
       const std::string& ice_ufrag,
       const std::string& ice_pwd) {
-    std::unique_ptr<PortAllocatorSession> session = allocator_->CreateSession(
-        sid, content_name, component, ice_ufrag, ice_pwd);
+    std::unique_ptr<PortAllocatorSession> session =
+        allocator_->CreateSession(content_name, component, ice_ufrag, ice_pwd);
     session->SignalPortReady.connect(this,
                                      &BasicPortAllocatorTest::OnPortReady);
     session->SignalPortsPruned.connect(this,