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

webrtc/api/peerconnectioninterface.h

Index: webrtc/api/peerconnectioninterface.h
diff --git a/webrtc/api/peerconnectioninterface.h b/webrtc/api/peerconnectioninterface.h
index d4daf2435e3ac7de78092579413fbc4aa41bd7dc..242d42aa32a333d724871701f29b3347ba3f2df0 100644
--- a/webrtc/api/peerconnectioninterface.h
+++ b/webrtc/api/peerconnectioninterface.h
@@ -299,6 +299,9 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
       }
     }
 
+    bool operator==(const RTCConfiguration& o) const;
+    bool operator!=(const RTCConfiguration& o) const;
+
     bool dscp() { return media_config.enable_dscp; }
     void set_dscp(bool enable) { media_config.enable_dscp = enable; }
 
@@ -372,6 +375,9 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
     // If true, ICE role is redetermined when peerconnection sets a local
     // transport description that indicates an ICE restart.
     bool redetermine_role_on_ice_restart = true;
+    //
+    // Don't forget to update operator== if adding something.
+    //
   };
 
   struct RTCOfferAnswerOptions {
@@ -530,15 +536,33 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
   virtual PeerConnectionInterface::RTCConfiguration GetConfiguration() {
     return PeerConnectionInterface::RTCConfiguration();
   }
+
   // Sets the PeerConnection's global configuration to |config|.
+  //
+  // The members of |config| that may be changed are |type|, |servers|,
+  // |ice_candidate_pool_size| and |prune_turn_ports| (though the candidate
+  // pool size can't be changed after the first call to SetLocalDescription).
+  // Note that this means the BUNDLE and RTCP-multiplexing policies cannot be
+  // changed with this method.
+  //
   // Any changes to STUN/TURN servers or ICE candidate policy will affect the
   // next gathering phase, and cause the next call to createOffer to generate
-  // new ICE credentials. Note that the BUNDLE and RTCP-multiplexing policies
-  // cannot be changed with this method.
+  // new ICE credentials, as described in JSEP. This also occurs when
+  // |prune_turn_ports| changes, for the same reasoning.
+  //
+  // If an error occurs, returns false and populates |error| if non-null:
+  // - INVALID_MODIFICATION if |config| contains a modified parameter other
+  //   than one of the parameters listed above.
+  // - INVALID_RANGE if |ice_candidate_pool_size| is out of range.
+  // - SYNTAX_ERROR if parsing an ICE server URL failed.
+  // - INVALID_PARAMETER if a TURN server is missing |username| or |password|.
+  // - INTERNAL_ERROR if an unexpected error occurred.
+  //
   // TODO(deadbeef): Make this pure virtual once all Chrome subclasses of
   // PeerConnectionInterface implement it.
   virtual bool SetConfiguration(
-      const PeerConnectionInterface::RTCConfiguration& config) {
+      const PeerConnectionInterface::RTCConfiguration& config,
+      RtcError* error = nullptr) {
     return false;
   }
   // Provides a remote candidate to the ICE Agent.