Relanding: Implement RTCConfiguration.iceCandidatePoolSize.

webrtc/p2p/base/portallocator.cc

Index: webrtc/p2p/base/portallocator.cc
diff --git a/webrtc/p2p/base/portallocator.cc b/webrtc/p2p/base/portallocator.cc
index 5c4243abf6b66e07c845448c24eed398e49edd02..8f296cbe5cb4e663609e76a81a67264a355a66d4 100644
--- a/webrtc/p2p/base/portallocator.cc
+++ b/webrtc/p2p/base/portallocator.cc
@@ -18,14 +18,51 @@ PortAllocatorSession::PortAllocatorSession(const std::string& content_name,
                                            const std::string& ice_ufrag,
                                            const std::string& ice_pwd,
                                            uint32_t flags)
-    : content_name_(content_name),
-      component_(component),
-      flags_(flags),
+    : flags_(flags),
       generation_(0),
+      content_name_(content_name),
+      component_(component),
       ice_ufrag_(ice_ufrag),
       ice_pwd_(ice_pwd) {
-  RTC_DCHECK(!ice_ufrag.empty());
-  RTC_DCHECK(!ice_pwd.empty());
+  // Pooled sessions are allowed to be created with empty content name,
+  // component, ufrag and password.
+  RTC_DCHECK(ice_ufrag.empty() == ice_pwd.empty());
+}
+
+void PortAllocator::SetConfiguration(
+    const ServerAddresses& stun_servers,
+    const std::vector<RelayServerConfig>& turn_servers,
+    int candidate_pool_size) {
+  bool ice_servers_changed =
+      (stun_servers != stun_servers_ || turn_servers != turn_servers_);
+  stun_servers_ = stun_servers;
+  turn_servers_ = turn_servers;
+
+  // If ICE servers changed, throw away any existing pooled sessions and create
+  // new ones.
+  if (ice_servers_changed) {
+    pooled_sessions_.clear();
+    allocated_pooled_sessions_ = 0;
+  }
+
+  // If |size| is less than the number of allocated sessions, get rid of the
+  // extras.
+  while (allocated_pooled_sessions_ > candidate_pool_size &&
+         !pooled_sessions_.empty()) {
+    pooled_sessions_.front().reset(nullptr);
+    pooled_sessions_.pop_front();
+    --allocated_pooled_sessions_;
+  }
+  // If |size| is greater than the number of allocated sessions, create new
+  // sessions.
+  while (allocated_pooled_sessions_ < candidate_pool_size) {
+    PortAllocatorSession* pooled_session = CreateSessionInternal("", 0, "", "");
+    pooled_session->StartGettingPorts();
+    pooled_sessions_.push_back(
+        std::unique_ptr<PortAllocatorSession>(pooled_session));
+    ++allocated_pooled_sessions_;
+  }
+  candidate_pool_size_ = candidate_pool_size;
 }
 
 PortAllocatorSession* PortAllocator::CreateSession(
@@ -37,4 +74,27 @@ PortAllocatorSession* PortAllocator::CreateSession(
   return CreateSessionInternal(content_name, component, ice_ufrag, ice_pwd);
 }
 
+PortAllocatorSession* PortAllocator::GetPooledSession(
+    const std::string& content_name,
+    int component,
+    const std::string& ice_ufrag,
+    const std::string& ice_pwd) {
+  RTC_DCHECK(!ice_ufrag.empty());
+  RTC_DCHECK(!ice_pwd.empty());
+  if (pooled_sessions_.empty()) {
+    return nullptr;
+  }
+  PortAllocatorSession* ret = pooled_sessions_.front().release();
+  ret->SetTransportInformation(content_name, component, ice_ufrag, ice_pwd);
+  pooled_sessions_.pop_front();
+  return ret;
+}
+
+const PortAllocatorSession* PortAllocator::PeekPooledSession() const {
+  if (pooled_sessions_.empty()) {
+    return nullptr;
+  }
+  return pooled_sessions_.front().get();
+}
+
 }  // namespace cricket