Fix side-effect in DCHECK that breaks another DCHECK in JingleSession.

DCHECK(!channels_[name]) adds NULL channel with |name| into the
map, which was breaking DCHECK in JingleSession destructor. Replaced
with another DCHECK that doesn't have side-effects. Added unittest
to catch this problem.
Also removed no-op line from ~JingleSession().

Review URL: https://codereview.chromium.org/594743002

Cr-Commit-Position: refs/heads/master@{#296224}

remoting/protocol/jingle_session.cc

@@ -85,7 +85,6 @@ JingleSession::~JingleSession() {
   STLDeleteContainerPointers(transport_info_requests_.begin(),
                              transport_info_requests_.end());
 
-  channel_multiplexer_.reset();
   DCHECK(channels_.empty());
 
   session_manager_->SessionDestroyed(this);
@@ -274,7 +273,7 @@ void JingleSession::CancelChannelCreation(const std::string& name) {
   if (it != channels_.end()) {
     DCHECK(!it->second->is_connected());
     delete it->second;
-    DCHECK(!channels_[name]);
+    DCHECK(channels_.find(name) == channels_.end());
   }
 }
 

remoting/protocol/jingle_session_unittest.cc

@@ -521,5 +521,19 @@ TEST_F(JingleSessionTest, TestFailedChannelAuth) {
   EXPECT_TRUE(!host_socket_.get());
 }
 
+TEST_F(JingleSessionTest, TestCancelChannelCreation) {
+  CreateSessionManagers(1, FakeAuthenticator::REJECT_CHANNEL);
+  ASSERT_NO_FATAL_FAILURE(
+      InitiateConnection(1, FakeAuthenticator::ACCEPT, false));
+
+  client_session_->GetTransportChannelFactory()->CreateChannel(
+      kChannelName, base::Bind(&JingleSessionTest::OnClientChannelCreated,
+                               base::Unretained(this)));
+  client_session_->GetTransportChannelFactory()->CancelChannelCreation(
+      kChannelName);
+
+  EXPECT_TRUE(!client_socket_.get());
+}
+
 }  // namespace protocol
 }  // namespace remoting