--- a/dom/base/ChromeUtils.cpp
+++ b/dom/base/ChromeUtils.cpp
@@ -6,17 +6,16 @@
 
 #include "ChromeUtils.h"
 
 #include "jsfriendapi.h"
 #include "WrapperFactory.h"
 
 #include "mozilla/Base64.h"
 #include "mozilla/BasePrincipal.h"
-#include "mozilla/CycleCollectedJSRuntime.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/dom/IdleDeadline.h"
 #include "mozilla/dom/UnionTypes.h"
 #include "mozilla/dom/WindowBinding.h" // For IdleRequestCallback/Options
 #include "nsThreadUtils.h"
 
 namespace mozilla {
 namespace dom {
@@ -429,37 +428,10 @@ ChromeUtils::IsOriginAttributesEqual(con
                                      const dom::OriginAttributesDictionary& aB)
 {
   return aA.mAppId == aB.mAppId &&
          aA.mInIsolatedMozBrowser == aB.mInIsolatedMozBrowser &&
          aA.mUserContextId == aB.mUserContextId &&
          aA.mPrivateBrowsingId == aB.mPrivateBrowsingId;
 }
 
-#ifdef NIGHTLY_BUILD
-/* static */ void
-ChromeUtils::GetRecentJSDevError(GlobalObject& aGlobal,
-                                JS::MutableHandleValue aRetval,
-                                ErrorResult& aRv)
-{
-  aRetval.setUndefined();
-  auto runtime = CycleCollectedJSRuntime::Get();
-  MOZ_ASSERT(runtime);
-
-  auto cx = aGlobal.Context();
-  if (!runtime->GetRecentDevError(cx, aRetval)) {
-    aRv.NoteJSContextException(cx);
-    return;
-  }
-}
-
-/* static */ void
-ChromeUtils::ClearRecentJSDevError(GlobalObject&)
-{
-  auto runtime = CycleCollectedJSRuntime::Get();
-  MOZ_ASSERT(runtime);
-
-  runtime->ClearRecentDevError();
-}
-#endif // NIGHTLY_BUILD
-
 } // namespace dom
 } // namespace mozilla

--- a/dom/base/ChromeUtils.h
+++ b/dom/base/ChromeUtils.h
@@ -143,20 +143,14 @@ public:
                            JS::HandleObject aTarget,
                            JS::MutableHandleObject aRetval,
                            ErrorResult& aRv);
 
   static void IdleDispatch(const GlobalObject& global,
                            IdleRequestCallback& callback,
                            const IdleRequestOptions& options,
                            ErrorResult& aRv);
-
-  static void GetRecentJSDevError(GlobalObject& aGlobal,
-                                  JS::MutableHandleValue aRetval,
-                                  ErrorResult& aRv);
-
-  static void ClearRecentJSDevError(GlobalObject& aGlobal);
 };
 
 } // namespace dom
 } // namespace mozilla
 
 #endif // mozilla_dom_ChromeUtils__

--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -10987,26 +10987,28 @@ nsContentUtils::IsOverridingWindowName(c
 #define EXTRACT_EXN_VALUES(T, ...)                                \
   ExtractExceptionValues<mozilla::dom::prototypes::id::T,         \
                          T##Binding::NativeType, T>(__VA_ARGS__).isOk()
 
 template <prototypes::ID PrototypeID, class NativeType, typename T>
 static Result<Ok, nsresult>
 ExtractExceptionValues(JSContext* aCx,
                        JS::HandleObject aObj,
-                       nsAString& aSourceSpecOut,
+                       nsACString& aSourceSpecOut,
                        uint32_t* aLineOut,
                        uint32_t* aColumnOut,
                        nsString& aMessageOut)
 {
   RefPtr<T> exn;
   MOZ_TRY((UnwrapObject<PrototypeID, NativeType>(aObj, exn)));
 
-  exn->GetFilename(aCx, aSourceSpecOut);
-  if (!aSourceSpecOut.IsEmpty()) {
+  nsAutoString filename;
+  exn->GetFilename(aCx, filename);
+  if (!filename.IsEmpty()) {
+    CopyUTF16toUTF8(filename, aSourceSpecOut);
     *aLineOut = exn->LineNumber(aCx);
     *aColumnOut = exn->ColumnNumber();
   }
 
   exn->GetName(aMessageOut);
   aMessageOut.AppendLiteral(": ");
 
   nsAutoString message;
@@ -11018,29 +11020,16 @@ ExtractExceptionValues(JSContext* aCx,
 /* static */ void
 nsContentUtils::ExtractErrorValues(JSContext* aCx,
                                    JS::Handle<JS::Value> aValue,
                                    nsACString& aSourceSpecOut,
                                    uint32_t* aLineOut,
                                    uint32_t* aColumnOut,
                                    nsString& aMessageOut)
 {
-  nsAutoString sourceSpec;
-  ExtractErrorValues(aCx, aValue, sourceSpec, aLineOut, aColumnOut, aMessageOut);
-  CopyUTF16toUTF8(sourceSpec, aSourceSpecOut);
-}
-
-/* static */ void
-nsContentUtils::ExtractErrorValues(JSContext* aCx,
-                                   JS::Handle<JS::Value> aValue,
-                                   nsAString& aSourceSpecOut,
-                                   uint32_t* aLineOut,
-                                   uint32_t* aColumnOut,
-                                   nsString& aMessageOut)
-{
   MOZ_ASSERT(aLineOut);
   MOZ_ASSERT(aColumnOut);
 
   if (aValue.isObject()) {
     JS::Rooted<JSObject*> obj(aCx, &aValue.toObject());
 
     // Try to process as an Error object.  Use the file/line/column values
     // from the Error as they will be more specific to the root cause of
@@ -11051,17 +11040,17 @@ nsContentUtils::ExtractErrorValues(JSCon
       // this report anywhere.
       RefPtr<xpc::ErrorReport> report = new xpc::ErrorReport();
       report->Init(err,
                    "<unknown>", // toString result
                    false,       // chrome
                    0);          // window ID
 
       if (!report->mFileName.IsEmpty()) {
-        aSourceSpecOut = report->mFileName;
+        CopyUTF16toUTF8(report->mFileName, aSourceSpecOut);
         *aLineOut = report->mLineNumber;
         *aColumnOut = report->mColumn;
       }
       aMessageOut.Assign(report->mErrorMsg);
     }
 
     // Next, try to unwrap the rejection value as a DOMException.
     else if (EXTRACT_EXN_VALUES(DOMException, aCx, obj, aSourceSpecOut,

--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -1131,24 +1131,16 @@ public:
    * Helper function that generates a UUID.
    */
   static nsresult GenerateUUIDInPlace(nsID& aUUID);
 
   static bool PrefetchPreloadEnabled(nsIDocShell* aDocShell);
 
   static void
   ExtractErrorValues(JSContext* aCx, JS::Handle<JS::Value> aValue,
-                     nsAString& aSourceSpecOut, uint32_t *aLineOut,
-                     uint32_t *aColumnOut, nsString& aMessageOut);
-
-  // Variant on `ExtractErrorValues` with a `nsACString`. This
-  // method is provided for backwards compatibility. Prefer the
-  // faster method above for your code.
-  static void
-  ExtractErrorValues(JSContext* aCx, JS::Handle<JS::Value> aValue,
                      nsACString& aSourceSpecOut, uint32_t *aLineOut,
                      uint32_t *aColumnOut, nsString& aMessageOut);
 
   /**
    * Helper function to tell if user ever enabled DevTools explicitely.
    * Allows making DevTools related API no-op until user do so.
    */
   static bool DevToolsEnabled(JSContext* aCx);

deleted file mode 100644
--- a/dom/base/test/unit/test_js_dev_error_interceptor.js
+++ /dev/null
@@ -1,57 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-function errors() {
-    return [
-        // The following two errors MUST NOT be captured.
-        new Error("This is an error: " + Math.random()),
-        new RangeError("This is a RangeError: " + Math.random()),
-        "This is a string: " + Math.random(),
-        null,
-        undefined,
-        Math.random(),
-        {},
-
-        // The following errors MUST be captured.
-        new TypeError("This is a TypeError: " + Math.random()),
-        new SyntaxError("This is a SyntaxError: " + Math.random()),
-        new ReferenceError("This is a ReferenceError: " + Math.random())
-    ]
-}
-
-function isDeveloperError(e) {
-    if (e == null || typeof e != "object") {
-        return false;
-    }
-
-    return e.constructor == TypeError
-        || e.constructor == SyntaxError
-        || e.constructor == ReferenceError;
-}
-
-function run_test() {
-    ChromeUtils.clearRecentJSDevError();
-    Assert.equal(ChromeUtils.recentJSDevError, undefined);
-
-    for (let exn of errors()) {
-        ChromeUtils.clearRecentJSDevError();
-        try {
-            throw exn;
-        } catch (e) {
-            // Discard error.
-        }
-        do_print(`Threw "${exn}", logged "${ChromeUtils.recentJSDevError}`);
-        if (isDeveloperError(exn)) {
-            Assert.equal(ChromeUtils.recentJSDevError.message, "" + exn);
-        } else {
-            Assert.equal(ChromeUtils.recentJSDevError, undefined);
-        }
-        ChromeUtils.clearRecentJSDevError();
-        Assert.equal(ChromeUtils.recentJSDevError, undefined);
-    }
-};
-

--- a/dom/base/test/unit/xpcshell.ini
+++ b/dom/base/test/unit/xpcshell.ini
@@ -49,12 +49,9 @@ head = head_xml.js
 head = head_xml.js
 [test_xml_serializer.js]
 head = head_xml.js
 [test_xmlserializer.js]
 [test_cancelPrefetch.js]
 [test_chromeutils_base64.js]
 [test_generate_xpath.js]
 head = head_xml.js
-[test_js_dev_error_interceptor.js]
-# This feature is implemented only in NIGHTLY.
-run-if = nightly_build
 

--- a/dom/webidl/ChromeUtils.webidl
+++ b/dom/webidl/ChromeUtils.webidl
@@ -84,50 +84,16 @@ namespace ChromeUtils {
    * @param string The string to decode.
    * @param options Additional decoding options.
    * @returns The decoded buffer.
    */
   [Throws, NewObject]
   ArrayBuffer base64URLDecode(ByteString string,
                               Base64URLDecodeOptions options);
 
-#ifdef NIGHTLY_BUILD
-
-  /**
-   * If the chrome code has thrown a JavaScript Dev Error
-   * in the current JSRuntime. the first such error, or `undefined`
-   * otherwise.
-   *
-   * A JavaScript Dev Error is an exception thrown by JavaScript
-   * code that matches both conditions:
-   * - it was thrown by chrome code;
-   * - it is either a `ReferenceError`, a `TypeError` or a `SyntaxError`.
-   *
-   * Such errors are stored regardless of whether they have been
-   * caught.
-   *
-   * This mechanism is designed to help ensure that the code of
-   * Firefox is free from Dev Errors, even if they are accidentally
-   * caught by clients.
-   *
-   * The object returned is not an exception. It has fields:
-   * - DOMString stack
-   * - DOMString filename
-   * - DOMString lineNumber
-   * - DOMString message
-   */
-  [Throws]
-  readonly attribute any recentJSDevError;
-
-  /**
-   * Reset `recentJSDevError` to `undefined` for the current JSRuntime.
-   */
-  void clearRecentJSDevError();
-#endif // NIGHTLY_BUILD
-
   /**
    * IF YOU ADD NEW METHODS HERE, MAKE SURE THEY ARE THREAD-SAFE.
    */
 };
 
 /**
  * Additional ChromeUtils methods that are _not_ thread-safe, and hence not
  * exposed in workers.

--- a/dom/webidl/moz.build
+++ b/dom/webidl/moz.build
@@ -358,17 +358,16 @@ with Files("WindowOrWorkerGlobalScope.we
 with Files("Worker*"):
     BUG_COMPONENT = ("Core", "DOM: Workers")
 
 GENERATED_WEBIDL_FILES = [
     'CSS2Properties.webidl',
 ]
 
 PREPROCESSED_WEBIDL_FILES = [
-    'ChromeUtils.webidl',
     'Navigator.webidl',
     'Node.webidl',
     'Window.webidl',
 ]
 
 WEBIDL_FILES = [
     'AbortController.webidl',
     'AbortSignal.webidl',
@@ -421,16 +420,17 @@ WEBIDL_FILES = [
     'CDATASection.webidl',
     'ChannelMergerNode.webidl',
     'ChannelSplitterNode.webidl',
     'ChannelWrapper.webidl',
     'CharacterData.webidl',
     'CheckerboardReportService.webidl',
     'ChildNode.webidl',
     'ChromeNodeList.webidl',
+    'ChromeUtils.webidl',
     'Client.webidl',
     'Clients.webidl',
     'ClipboardEvent.webidl',
     'CommandEvent.webidl',
     'Comment.webidl',
     'CompositionEvent.webidl',
     'Console.webidl',
     'ConstantSourceNode.webidl',

--- a/js/src/jsapi-tests/moz.build
+++ b/js/src/jsapi-tests/moz.build
@@ -132,23 +132,16 @@ if CONFIG['ENABLE_ION']:
         'testJitRValueAlloc.cpp',
     ]
 
 if CONFIG['ENABLE_STREAMS']:
     UNIFIED_SOURCES += [
         'testReadableStream.cpp',
     ]
 
-
-if CONFIG['NIGHTLY_BUILD']:
-    # The Error interceptor only exists on Nightly.
-    UNIFIED_SOURCES += [
-        'testErrorInterceptor.cpp',
-    ]
-
 if CONFIG['JS_BUILD_BINAST'] and CONFIG['JS_STANDALONE']:
     # Standalone builds leave the source directory untouched,
     # which lets us run tests with the data files intact.
     # Otherwise, in the current state of the build system,
     # we can't have data files in js/src tests.
     UNIFIED_SOURCES += [
         'testBinASTReader.cpp',
         'testBinTokenReaderTester.cpp'

deleted file mode 100644
--- a/js/src/jsapi-tests/testErrorInterceptor.cpp
+++ /dev/null
@@ -1,143 +0,0 @@
-#include "jsapi.h"
-
-#include "jsapi-tests/tests.h"
-
-#include "vm/StringBuffer.h"
-
-// Tests for JS_GetErrorInterceptorCallback and JS_SetErrorInterceptorCallback.
-
-
-namespace {
-const double EXN_VALUE = 3.14;
-
-static JS::PersistentRootedString gLatestMessage;
-
-// An interceptor that stores the error in `gLatestMessage`.
-struct SimpleInterceptor: JSErrorInterceptor {
-    virtual void interceptError(JSContext* cx, const JS::Value& val) override {
-        js::StringBuffer buffer(cx);
-        if (!ValueToStringBuffer(cx, val, buffer))
-            MOZ_CRASH("Could not convert to string buffer");
-        gLatestMessage = buffer.finishString();
-        if (!gLatestMessage)
-            MOZ_CRASH("Could not convert to string");
-    }
-};
-
-bool equalStrings(JSContext* cx, JSString* a, JSString* b) {
-    int32_t result = 0;
-    if (!JS_CompareStrings(cx, a, b, &result))
-        MOZ_CRASH("Could not compare strings");
-    return result == 0;
-}
-}
-
-BEGIN_TEST(testErrorInterceptor)
-{
-    // Run the following snippets.
-    const char* SAMPLES[] = {
-        "throw new Error('I am an Error')\0",
-        "throw new TypeError('I am a TypeError')\0",
-        "throw new ReferenceError('I am a ReferenceError')\0",
-        "throw new SyntaxError('I am a SyntaxError')\0",
-        "throw 5\0",
-        "undefined[0]\0",
-        "foo[0]\0",
-        "b[\0",
-    };
-    // With the simpleInterceptor, we should end up with the following error:
-    const char* TO_STRING[] = {
-        "Error: I am an Error\0",
-        "TypeError: I am a TypeError\0",
-        "ReferenceError: I am a ReferenceError\0",
-        "SyntaxError: I am a SyntaxError\0",
-        "5\0",
-        "TypeError: undefined has no properties\0",
-        "ReferenceError: foo is not defined\0",
-        "SyntaxError: expected expression, got end of script\0",
-    };
-    MOZ_ASSERT(mozilla::ArrayLength(SAMPLES) == mozilla::ArrayLength(TO_STRING));
-
-
-    // Save original callback.
-    JSErrorInterceptor* original = JS_GetErrorInterceptorCallback(cx->runtime());
-    gLatestMessage.init(cx);
-
-    // Test without callback.
-    JS_SetErrorInterceptorCallback(cx->runtime(), nullptr);
-    CHECK(gLatestMessage == nullptr);
-
-    for (auto sample: SAMPLES) {
-        if (execDontReport(sample, __FILE__, __LINE__))
-            MOZ_CRASH("This sample should have failed");
-        CHECK(JS_IsExceptionPending(cx));
-        CHECK(gLatestMessage == nullptr);
-        JS_ClearPendingException(cx);
-    }
-
-    // Test with callback.
-    SimpleInterceptor simpleInterceptor;
-    JS_SetErrorInterceptorCallback(cx->runtime(), &simpleInterceptor);
-
-    // Test that we return the right callback.
-    CHECK_EQUAL(JS_GetErrorInterceptorCallback(cx->runtime()), &simpleInterceptor);
-
-    // This shouldn't cause any error.
-    EXEC("function bar() {}");
-    CHECK(gLatestMessage == nullptr);
-
-    // Test error throwing with a callback that succeeds.
-    for (size_t i = 0; i < mozilla::ArrayLength(SAMPLES); ++i) {
-        // This should cause the appropriate error.
-        if (execDontReport(SAMPLES[i], __FILE__, __LINE__))
-            MOZ_CRASH("This sample should have failed");
-        CHECK(JS_IsExceptionPending(cx));
-
-        // Check result of callback.
-        CHECK(gLatestMessage != nullptr);
-        CHECK(js::StringEqualsAscii(&gLatestMessage->asLinear(), TO_STRING[i]));
-
-        // Check the final error.
-        JS::RootedValue exn(cx);
-        CHECK(JS_GetPendingException(cx, &exn));
-        JS_ClearPendingException(cx);
-
-        js::StringBuffer buffer(cx);
-        CHECK(ValueToStringBuffer(cx, exn, buffer));
-        CHECK(equalStrings(cx, buffer.finishString(), gLatestMessage));
-
-        // Cleanup.
-        gLatestMessage = nullptr;
-    }
-
-    // Test again without callback.
-    JS_SetErrorInterceptorCallback(cx->runtime(), nullptr);
-    for (size_t i = 0; i < mozilla::ArrayLength(SAMPLES); ++i) {
-        if (execDontReport(SAMPLES[i], __FILE__, __LINE__))
-            MOZ_CRASH("This sample should have failed");
-        CHECK(JS_IsExceptionPending(cx));
-
-        // Check that the callback wasn't called.
-        CHECK(gLatestMessage == nullptr);
-
-        // Check the final error.
-        JS::RootedValue exn(cx);
-        CHECK(JS_GetPendingException(cx, &exn));
-        JS_ClearPendingException(cx);
-
-        js::StringBuffer buffer(cx);
-        CHECK(ValueToStringBuffer(cx, exn, buffer));
-        CHECK(js::StringEqualsAscii(buffer.finishString(), TO_STRING[i]));
-
-        // Cleanup.
-        gLatestMessage = nullptr;
-    }
-
-    // Cleanup
-    JS_SetErrorInterceptorCallback(cx->runtime(), original);
-    gLatestMessage = nullptr;
-    JS_ClearPendingException(cx);
-
-    return true;
-}
-END_TEST(testErrorInterceptor)

--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -648,50 +648,16 @@ JS_SetSizeOfIncludingThisCompartmentCall
 }
 
 JS_PUBLIC_API(void)
 JS_SetCompartmentNameCallback(JSContext* cx, JSCompartmentNameCallback callback)
 {
     cx->runtime()->compartmentNameCallback = callback;
 }
 
-#if defined(NIGHTLY_BUILD)
-JS_PUBLIC_API(void)
-JS_SetErrorInterceptorCallback(JSRuntime* rt, JSErrorInterceptor* callback)
-{
-    rt->errorInterception.interceptor = callback;
-}
-
-JS_PUBLIC_API(JSErrorInterceptor*)
-JS_GetErrorInterceptorCallback(JSRuntime* rt)
-{
-    return rt->errorInterception.interceptor;
-}
-
-JS_PUBLIC_API(Maybe<JSExnType>)
-JS_GetErrorType(const JS::Value& val)
-{
-    // All errors are objects.
-    if (!val.isObject())
-        return mozilla::Nothing();
-
-    const JSObject& obj = val.toObject();
-
-    // All errors are `ErrorObject`.
-    if (!obj.is<js::ErrorObject>()) {
-        // Not one of the primitive errors.
-        return mozilla::Nothing();
-    }
-
-    const js::ErrorObject& err = obj.as<js::ErrorObject>();
-    return mozilla::Some(err.type());
-}
-
-#endif // defined(NIGHTLY_BUILD)
-
 JS_PUBLIC_API(void)
 JS_SetWrapObjectCallbacks(JSContext* cx, const JSWrapObjectCallbacks* callbacks)
 {
     cx->runtime()->wrapObjectCallbacks = callbacks;
 }
 
 JS_PUBLIC_API(void)
 JS_SetExternalStringSizeofCallback(JSContext* cx, JSExternalStringSizeofCallback callback)

--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -675,28 +675,16 @@ typedef void
  * that corresponds to the size of the allocation that will be released by the
  * JSStringFinalizer passed to JS_NewExternalString for this string.
  *
  * Implementations of this callback MUST NOT do anything that can cause GC.
  */
 using JSExternalStringSizeofCallback =
     size_t (*)(JSString* str, mozilla::MallocSizeOf mallocSizeOf);
 
-/**
- * Callback used to intercept JavaScript errors.
- */
-struct JSErrorInterceptor {
-    /**
-     * This method is called whenever an error has been raised from JS code.
-     *
-     * This method MUST be infallible.
-     */
-    virtual void interceptError(JSContext* cx, const JS::Value& error) = 0;
-};
-
 /************************************************************************/
 
 static MOZ_ALWAYS_INLINE JS::Value
 JS_NumberValue(double d)
 {
     int32_t i;
     d = JS::CanonicalizeNaN(d);
     if (mozilla::NumberIsInt32(d, &i))
@@ -1334,43 +1322,16 @@ extern JS_PUBLIC_API(void)
 JS_SetCompartmentNameCallback(JSContext* cx, JSCompartmentNameCallback callback);
 
 extern JS_PUBLIC_API(void)
 JS_SetWrapObjectCallbacks(JSContext* cx, const JSWrapObjectCallbacks* callbacks);
 
 extern JS_PUBLIC_API(void)
 JS_SetExternalStringSizeofCallback(JSContext* cx, JSExternalStringSizeofCallback callback);
 
-#if defined(NIGHTLY_BUILD)
-
-// Set a callback that will be called whenever an error
-// is thrown in this runtime. This is designed as a mechanism
-// for logging errors. Note that the VM makes no attempt to sanitize
-// the contents of the error (so it may contain private data)
-// or to sort out among errors (so it may not be the error you
-// are interested in or for the component in which you are
-// interested).
-//
-// If the callback sets a new error, this new error
-// will replace the original error.
-//
-// May be `nullptr`.
-extern JS_PUBLIC_API(void)
-JS_SetErrorInterceptorCallback(JSRuntime*, JSErrorInterceptor* callback);
-
-extern JS_PUBLIC_API(JSErrorInterceptor*)
-JS_GetErrorInterceptorCallback(JSRuntime*);
-
-// Examine a value to determine if it is one of the built-in Error types.
-// If so, return the error type.
-extern JS_PUBLIC_API(mozilla::Maybe<JSExnType>)
-JS_GetErrorType(const JS::Value& val);
-
-#endif // defined(NIGHTLY_BUILD)
-
 extern JS_PUBLIC_API(void)
 JS_SetCompartmentPrivate(JSCompartment* compartment, void* data);
 
 extern JS_PUBLIC_API(void*)
 JS_GetCompartmentPrivate(JSCompartment* compartment);
 
 extern JS_PUBLIC_API(void)
 JS_SetZoneUserData(JS::Zone* zone, void* data);

--- a/js/src/jscntxtinlines.h
+++ b/js/src/jscntxtinlines.h
@@ -429,41 +429,16 @@ inline void
 JSContext::minorGC(JS::gcreason::Reason reason)
 {
     runtime()->gc.minorGC(reason);
 }
 
 inline void
 JSContext::setPendingException(const js::Value& v)
 {
-#if defined(NIGHTLY_BUILD)
-    do {
-        // Do not intercept exceptions if we are already
-        // in the exception interceptor. That would lead
-        // to infinite recursion.
-        if (this->runtime()->errorInterception.isExecuting)
-            break;
-
-        // Check whether we have an interceptor at all.
-        if (!this->runtime()->errorInterception.interceptor)
-            break;
-
-        // Make sure that we do not call the interceptor from within
-        // the interceptor.
-        this->runtime()->errorInterception.isExecuting = true;
-
-        // The interceptor must be infallible.
-        const mozilla::DebugOnly<bool> wasExceptionPending = this->isExceptionPending();
-        this->runtime()->errorInterception.interceptor->interceptError(this, v);
-        MOZ_ASSERT(wasExceptionPending == this->isExceptionPending());
-
-        this->runtime()->errorInterception.isExecuting = false;
-    } while (false);
-#endif // defined(NIGHTLY_BUILD)
-
     // overRecursed_ is set after the fact by ReportOverRecursed.
     this->overRecursed_ = false;
     this->throwing = true;
     this->unwrappedException() = v;
     // We don't use assertSameCompartment here to allow
     // js::SetPendingExceptionCrossContext to work.
     MOZ_ASSERT_IF(v.isObject(), v.toObject().compartment() == compartment());
 }

--- a/js/src/vm/Runtime.h
+++ b/js/src/vm/Runtime.h
@@ -1076,40 +1076,16 @@ struct JSRuntime : public js::MallocProv
         wasmUnwindPC_ = nullptr;
     }
     void* wasmResumePC() const {
         return wasmResumePC_;
     }
     void* wasmUnwindPC() const {
         return wasmUnwindPC_;
     }
-
-  public:
-#if defined(NIGHTLY_BUILD)
-    // Support for informing the embedding of any error thrown.
-    // This mechanism is designed to let the embedding
-    // log/report/fail in case certain errors are thrown
-    // (e.g. SyntaxError, ReferenceError or TypeError
-    // in critical code).
-    struct ErrorInterceptionSupport {
-        ErrorInterceptionSupport()
-          : isExecuting(false)
-          , interceptor(nullptr)
-        { }
-
-        // true if the error interceptor is currently executing,
-        // false otherwise. Used to avoid infinite loops.
-        bool isExecuting;
-
-        // if non-null, any call to `setPendingException`
-        // in this runtime will trigger the call to `interceptor`
-        JSErrorInterceptor* interceptor;
-    };
-    ErrorInterceptionSupport errorInterception;
-#endif // defined(NIGHTLY_BUILD)
 };
 
 namespace js {
 
 inline void
 FreeOp::free_(void* p)
 {
     js_free(p);

--- a/xpcom/base/CycleCollectedJSRuntime.cpp
+++ b/xpcom/base/CycleCollectedJSRuntime.cpp
@@ -92,21 +92,16 @@
 #endif
 
 #include "nsIException.h"
 #include "nsIPlatformInfo.h"
 #include "nsThread.h"
 #include "nsThreadUtils.h"
 #include "xpcpublic.h"
 
-#ifdef NIGHTLY_BUILD
-// For performance reasons, we make the JS Dev Error Interceptor a Nightly-only feature.
-#define MOZ_JS_DEV_ERROR_INTERCEPTOR = 1
-#endif // NIGHTLY_BUILD
-
 using namespace mozilla;
 using namespace mozilla::dom;
 
 namespace mozilla {
 
 struct DeferredFinalizeFunctionHolder
 {
   DeferredFinalizeFunction run;
@@ -556,40 +551,30 @@ CycleCollectedJSRuntime::CycleCollectedJ
 
   static js::DOMCallbacks DOMcallbacks = {
     InstanceClassHasProtoAtDepth
   };
   SetDOMCallbacks(aCx, &DOMcallbacks);
   js::SetScriptEnvironmentPreparer(aCx, &mEnvironmentPreparer);
 
   JS::dbg::SetDebuggerMallocSizeOf(aCx, moz_malloc_size_of);
-
-#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR
-  JS_SetErrorInterceptorCallback(mJSRuntime, &mErrorInterceptor);
-#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR
 }
 
 void
 CycleCollectedJSRuntime::Shutdown(JSContext* cx)
 {
-#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR
-  mErrorInterceptor.Shutdown(mJSRuntime);
-#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR
   JS_RemoveExtraGCRootsTracer(cx, TraceBlackJS, this);
   JS_RemoveExtraGCRootsTracer(cx, TraceGrayJS, this);
 #ifdef DEBUG
   mShutdownCalled = true;
 #endif
 }
 
 CycleCollectedJSRuntime::~CycleCollectedJSRuntime()
 {
-#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR
-  mErrorInterceptor.Shutdown(mJSRuntime);
-#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR
   MOZ_COUNT_DTOR(CycleCollectedJSRuntime);
   MOZ_ASSERT(!mDeferredFinalizerTable.Count());
   MOZ_ASSERT(mShutdownCalled);
 }
 
 void
 CycleCollectedJSRuntime::AddContext(CycleCollectedJSContext* aContext)
 {
@@ -1567,118 +1552,8 @@ CycleCollectedJSRuntime::EnvironmentPrep
 CycleCollectedJSRuntime::Get()
 {
   auto context = CycleCollectedJSContext::Get();
   if (context) {
     return context->Runtime();
   }
   return nullptr;
 }
-
-#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR
-
-namespace js {
-extern void DumpValue(const JS::Value& val);
-}
-
-void
-CycleCollectedJSRuntime::ErrorInterceptor::Shutdown(JSRuntime* rt)
-{
-  JS_SetErrorInterceptorCallback(rt, nullptr);
-  mThrownError.reset();
-}
-
-/* virtual */ void
-CycleCollectedJSRuntime::ErrorInterceptor::interceptError(JSContext* cx, const JS::Value& exn)
-{
-  if (mThrownError) {
-    // We already have an error, we don't need anything more.
-    return;
-  }
-
-  if (!nsContentUtils::ThreadsafeIsSystemCaller(cx)) {
-    // We are only interested in chrome code.
-    return;
-  }
-
-  const auto type = JS_GetErrorType(exn);
-  if (!type) {
-    // This is not one of the primitive error types.
-    return;
-  }
-
-  switch (*type) {
-    case JSExnType::JSEXN_REFERENCEERR:
-    case JSExnType::JSEXN_SYNTAXERR:
-    case JSExnType::JSEXN_TYPEERR:
-      break;
-    default:
-      // Not one of the errors we are interested in.
-      return;
-  }
-
-  // Now copy the details of the exception locally.
-  // While copying the details of an exception could be expensive, in most runs,
-  // this will be done at most once during the execution of the process, so the
-  // total cost should be reasonable.
-  JS::RootedValue value(cx, exn);
-
-  ErrorDetails details;
-  details.mType = *type;
-  // If `exn` isn't an exception object, `ExtractErrorValues` could end up calling
-  // `toString()`, which could in turn end up throwing an error. While this should
-  // work, we want to avoid that complex use case.
-  // Fortunately, we have already checked above that `exn` is an exception object,
-  // so nothing such should happen.
-  nsContentUtils::ExtractErrorValues(cx, value, details.mFilename, &details.mLine, &details.mColumn, details.mMessage);
-
-  nsAutoCString stack;
-  JS::UniqueChars buf = JS::FormatStackDump(cx, nullptr, /* showArgs = */ false, /* showLocals = */ false, /* showThisProps = */ false);
-  stack.Append(buf.get());
-  CopyUTF8toUTF16(buf.get(), details.mStack);
-
-  mThrownError.emplace(Move(details));
-}
-
-void
-CycleCollectedJSRuntime::ClearRecentDevError()
-{
-  mErrorInterceptor.mThrownError.reset();
-}
-
-bool
-CycleCollectedJSRuntime::GetRecentDevError(JSContext*cx, JS::MutableHandle<JS::Value> error)
-{
-  if (!mErrorInterceptor.mThrownError) {
-    return true;
-  }
-
-  // Create a copy of the exception.
-  JS::RootedObject obj(cx, JS_NewPlainObject(cx));
-  if (!obj) {
-    return false;
-  }
-
-  JS::RootedValue message(cx);
-  JS::RootedValue filename(cx);
-  JS::RootedValue stack(cx);
-  if (!ToJSValue(cx, mErrorInterceptor.mThrownError->mMessage, &message) ||
-      !ToJSValue(cx, mErrorInterceptor.mThrownError->mFilename, &filename) ||
-      !ToJSValue(cx, mErrorInterceptor.mThrownError->mStack, &stack)) {
-    return false;
-  }
-
-  // Build the object.
-  const auto FLAGS = JSPROP_READONLY | JSPROP_ENUMERATE | JSPROP_PERMANENT;
-  if (!JS_DefineProperty(cx, obj, "message", message, FLAGS) ||
-      !JS_DefineProperty(cx, obj, "fileName", filename, FLAGS) ||
-      !JS_DefineProperty(cx, obj, "lineNumber", mErrorInterceptor.mThrownError->mLine, FLAGS) ||
-      !JS_DefineProperty(cx, obj, "stack", stack, FLAGS)) {
-    return false;
-  }
-
-  // Pass the result.
-  error.setObject(*obj);
-  return true;
-}
-#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR
-
-#undef MOZ_JS_DEV_ERROR_INTERCEPTOR

--- a/xpcom/base/CycleCollectedJSRuntime.h
+++ b/xpcom/base/CycleCollectedJSRuntime.h
@@ -323,21 +323,16 @@ public:
 
   // Get the current thread's CycleCollectedJSRuntime.  Returns null if there
   // isn't one.
   static CycleCollectedJSRuntime* Get();
 
   void AddContext(CycleCollectedJSContext* aContext);
   void RemoveContext(CycleCollectedJSContext* aContext);
 
-#ifdef NIGHTLY_BUILD
-  bool GetRecentDevError(JSContext* aContext, JS::MutableHandle<JS::Value> aError);
-  void ClearRecentDevError();
-#endif // defined(NIGHTLY_BUILD)
-
 private:
   LinkedList<CycleCollectedJSContext> mContexts;
 
   JSGCThingParticipant mGCThingCycleCollectorGlobal;
 
   JSZoneParticipant mJSZoneCycleCollectorGlobal;
 
   JSRuntime* mJSRuntime;
@@ -372,47 +367,16 @@ private:
   struct EnvironmentPreparer : public js::ScriptEnvironmentPreparer {
     void invoke(JS::HandleObject scope, Closure& closure) override;
   };
   EnvironmentPreparer mEnvironmentPreparer;
 
 #ifdef DEBUG
   bool mShutdownCalled;
 #endif
-
-#ifdef NIGHTLY_BUILD
-  // Implementation of the error interceptor.
-  // Built on nightly only to avoid any possible performance impact on release
-
-  struct ErrorInterceptor final : public JSErrorInterceptor {
-    virtual void interceptError(JSContext* cx, const JS::Value& val) override;
-    void Shutdown(JSRuntime* rt);
-
-    // Copy of the details of the exception.
-    // We store this rather than the exception itself to avoid dealing with complicated
-    // garbage-collection scenarios, e.g. a JSContext being killed while we still hold
-    // onto an exception thrown from it.
-    struct ErrorDetails {
-      nsString mFilename;
-      nsString mMessage;
-      nsString mStack;
-      JSExnType mType;
-      uint32_t mLine;
-      uint32_t mColumn;
-    };
-
-    // If we have encountered at least one developer error,
-    // the first error we have encountered. Otherwise, or
-    // if we have reset since the latest error, `None`.
-    Maybe<ErrorDetails> mThrownError;
-  };
-  ErrorInterceptor mErrorInterceptor;
-
-#endif // defined(NIGHTLY_BUILD)
-
 };
 
 void TraceScriptHolder(nsISupports* aHolder, JSTracer* aTracer);
 
 // Returns true if the JS::TraceKind is one the cycle collector cares about.
 inline bool AddToCCKind(JS::TraceKind aKind)
 {
   return aKind == JS::TraceKind::Object ||