Reland of: Adding error output param to SetConfiguration, using new RTCError type.

Most notably, will return "INVALID_MODIFICATION" if a field in the
configuration was modified and modification of that field isn't supported.

Also changing RTCError to a class that wraps an enum type, because it will
eventually need to hold other information (like SDP line number), to match
the RTCError that was recently added to the spec:
https://github.com/w3c/webrtc-pc/pull/850

BUG=webrtc:6916

Review-Url: https://codereview.webrtc.org/2587133004
Cr-Original-Commit-Position: refs/heads/master@{#15777}
Committed: https://chromium.googlesource.com/external/webrtc/+/7a5fa6cd6173adbe32aedc1aedc872478121f5ed
Review-Url: https://codereview.webrtc.org/2587133004
Cr-Commit-Position: refs/heads/master@{#16016}
diff --git a/webrtc/api/peerconnection.h b/webrtc/api/peerconnection.h
index 5269e3a..82dc8ed 100644
--- a/webrtc/api/peerconnection.h
+++ b/webrtc/api/peerconnection.h
@@ -54,10 +54,12 @@
                                cricket::MediaSessionOptions* session_options);
 
 // Parses the URLs for each server in |servers| to build |stun_servers| and
-// |turn_servers|.
-bool ParseIceServers(const PeerConnectionInterface::IceServers& servers,
-                     cricket::ServerAddresses* stun_servers,
-                     std::vector<cricket::RelayServerConfig>* turn_servers);
+// |turn_servers|. Can return SYNTAX_ERROR if the URL is malformed, or
+// INVALID_PARAMETER if a TURN server is missing |username| or |password|.
+RTCErrorType ParseIceServers(
+    const PeerConnectionInterface::IceServers& servers,
+    cricket::ServerAddresses* stun_servers,
+    std::vector<cricket::RelayServerConfig>* turn_servers);
 
 // PeerConnection implements the PeerConnectionInterface interface.
 // It uses WebRtcSession to implement the PeerConnection functionality.
@@ -137,7 +139,12 @@
                             SessionDescriptionInterface* desc) override;
   PeerConnectionInterface::RTCConfiguration GetConfiguration() override;
   bool SetConfiguration(
-      const PeerConnectionInterface::RTCConfiguration& configuration) override;
+      const PeerConnectionInterface::RTCConfiguration& configuration,
+      RTCError* error) override;
+  bool SetConfiguration(
+      const PeerConnectionInterface::RTCConfiguration& configuration) override {
+    return SetConfiguration(configuration, nullptr);
+  }
   bool AddIceCandidate(const IceCandidateInterface* candidate) override;
   bool RemoveIceCandidates(
       const std::vector<cricket::Candidate>& candidates) override;
@@ -373,9 +380,14 @@
 
   // Called when first configuring the port allocator.
   bool InitializePortAllocator_n(const RTCConfiguration& configuration);
-  // Called when SetConfiguration is called. Only a subset of the configuration
-  // is applied.
-  bool ReconfigurePortAllocator_n(const RTCConfiguration& configuration);
+  // Called when SetConfiguration is called to apply the supported subset
+  // of the configuration on the network thread.
+  bool ReconfigurePortAllocator_n(
+      const cricket::ServerAddresses& stun_servers,
+      const std::vector<cricket::RelayServerConfig>& turn_servers,
+      IceTransportsType type,
+      int candidate_pool_size,
+      bool prune_turn_ports);
 
   // Starts recording an Rtc EventLog using the supplied platform file.
   // This function should only be called from the worker thread.