Revert of Adding error output param to SetConfiguration, using new RTCError type. (patchset #4 id:60001 of https://codereview.webrtc.org/2587133004/ )

Reason for revert:
Broke chromium FYI bot because the chromium mock PC overrides the method whose signature is changing.

Also broke a downstream internal test, which I need to investigate further.

Original issue's description:
> 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-Commit-Position: refs/heads/master@{#15777}
> Committed: https://chromium.googlesource.com/external/webrtc/+/7a5fa6cd6173adbe32aedc1aedc872478121f5ed

TBR=pthatcher@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6916

Review-Url: https://codereview.webrtc.org/2600813002
Cr-Commit-Position: refs/heads/master@{#15778}
diff --git a/webrtc/api/peerconnectioninterface.h b/webrtc/api/peerconnectioninterface.h
index 1fac5c7..e81eee2 100644
--- a/webrtc/api/peerconnectioninterface.h
+++ b/webrtc/api/peerconnectioninterface.h
@@ -150,10 +150,9 @@
 typedef MetricsObserverInterface UMAObserver;
 
 // Enumeration to represent distinct classes of errors that an application
-// may wish to act upon differently. These roughly map to DOMExceptions or
-// RTCError "errorDetailEnum" values in the web API, as described in the
-// comments below.
-enum class RTCErrorType {
+// may wish to act upon differently. These roughly map to DOMExceptions in
+// the web API, as described in the comments below.
+enum class RtcError {
   // No error.
   NONE,
   // A supplied parameter is valid, but currently unsupported.
@@ -184,26 +183,9 @@
   INTERNAL_ERROR,
 };
 
-// Roughly corresponds to RTCError in the web api. Holds an error type and
-// possibly additional information specific to that error.
-//
-// Doesn't contain anything beyond a type now, but will in the future as more
-// errors are implemented.
-class RTCError {
- public:
-  RTCError() : type_(RTCErrorType::NONE) {}
-  explicit RTCError(RTCErrorType type) : type_(type) {}
-
-  RTCErrorType type() const { return type_; }
-  void set_type(RTCErrorType type) { type_ = type; }
-
- private:
-  RTCErrorType type_;
-};
-
 // Outputs the error as a friendly string.
 // Update this method when adding a new error type.
-std::ostream& operator<<(std::ostream& stream, RTCErrorType error);
+std::ostream& operator<<(std::ostream& stream, RtcError error);
 
 class PeerConnectionInterface : public rtc::RefCountInterface {
  public:
@@ -324,9 +306,6 @@
       }
     }
 
-    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; }
 
@@ -400,9 +379,6 @@
     // 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 {
@@ -580,33 +556,15 @@
   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, 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.
-  //
+  // new ICE credentials. Note that the BUNDLE and RTCP-multiplexing policies
+  // cannot be changed with this method.
   // TODO(deadbeef): Make this pure virtual once all Chrome subclasses of
   // PeerConnectionInterface implement it.
   virtual bool SetConfiguration(
-      const PeerConnectionInterface::RTCConfiguration& config,
-      RTCError* error = nullptr) {
+      const PeerConnectionInterface::RTCConfiguration& config) {
     return false;
   }
   // Provides a remote candidate to the ICE Agent.