diff --git a/dom/base/StructuredCloneHolder.cpp b/dom/base/StructuredCloneHolder.cpp
index 8f27f843d379..82a6e1f43b91 100644
--- a/dom/base/StructuredCloneHolder.cpp
+++ b/dom/base/StructuredCloneHolder.cpp
@@ -30,7 +30,6 @@
 #include "mozilla/dom/StructuredCloneTags.h"
 #include "mozilla/dom/SubtleCryptoBinding.h"
 #include "mozilla/dom/ToJSValue.h"
-#include "mozilla/dom/URLSearchParams.h"
 #include "mozilla/dom/WebCryptoCommon.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/ipc/BackgroundChild.h"
@@ -396,7 +395,7 @@ StructuredCloneHolder::ReadFullySerializableObjects(JSContext* aCx,
     return ReadStructuredCloneImageData(aCx, aReader);
   }
 
-  if (aTag == SCTAG_DOM_WEBCRYPTO_KEY || aTag == SCTAG_DOM_URLSEARCHPARAMS) {
+  if (aTag == SCTAG_DOM_WEBCRYPTO_KEY) {
     nsIGlobalObject *global = xpc::NativeGlobal(JS::CurrentGlobalOrNull(aCx));
     if (!global) {
       return nullptr;
@@ -405,20 +404,11 @@ StructuredCloneHolder::ReadFullySerializableObjects(JSContext* aCx,
     // Prevent the return value from being trashed by a GC during ~nsRefPtr.
     JS::Rooted<JSObject*> result(aCx);
     {
-      if (aTag == SCTAG_DOM_WEBCRYPTO_KEY) {
-        RefPtr<CryptoKey> key = new CryptoKey(global);
-        if (!key->ReadStructuredClone(aReader)) {
-         result = nullptr;
-        } else {
-          result = key->WrapObject(aCx, nullptr);
-        }
-      } else if (aTag == SCTAG_DOM_URLSEARCHPARAMS) {
-        RefPtr<URLSearchParams> usp = new URLSearchParams(global);
-       if (!usp->ReadStructuredClone(aReader)) {
-          result = nullptr;
-        } else {
-          result = usp->WrapObject(aCx, nullptr);
-        }
+      RefPtr<CryptoKey> key = new CryptoKey(global);
+      if (!key->ReadStructuredClone(aReader)) {
+        result = nullptr;
+      } else {
+        result = key->WrapObject(aCx, nullptr);
       }
     }
     return result;
@@ -514,15 +504,6 @@ StructuredCloneHolder::WriteFullySerializableObjects(JSContext* aCx,
     }
   }
 
-  // Handle URLSearchParams cloning
-  {
-    URLSearchParams* usp = nullptr;
-    if (NS_SUCCEEDED(UNWRAP_OBJECT(URLSearchParams, aObj, usp))) {
-      return JS_WriteUint32Pair(aWriter, SCTAG_DOM_URLSEARCHPARAMS, 0) &&
-             usp->WriteStructuredClone(aWriter);
-    }
-  }
-
   // Handle Key cloning
   {
     CryptoKey* key = nullptr;
diff --git a/dom/base/StructuredCloneTags.h b/dom/base/StructuredCloneTags.h
index 683a09228621..abba5567e162 100644
--- a/dom/base/StructuredCloneTags.h
+++ b/dom/base/StructuredCloneTags.h
@@ -54,9 +54,6 @@ enum StructuredCloneTags {
 
   SCTAG_DOM_DIRECTORY,
 
-  // This tag is used by both main thread and workers.
-  SCTAG_DOM_URLSEARCHPARAMS,
-
   SCTAG_DOM_MAX
 };
 
diff --git a/dom/url/URLSearchParams.cpp b/dom/url/URLSearchParams.cpp
index d9492f81c638..0eb207b68090 100644
--- a/dom/url/URLSearchParams.cpp
+++ b/dom/url/URLSearchParams.cpp
@@ -8,8 +8,6 @@
 #include "mozilla/dom/URLSearchParamsBinding.h"
 #include "mozilla/dom/EncodingUtils.h"
 #include "nsDOMString.h"
-#include "nsIInputStream.h"
-#include "nsStringStream.h"
 
 namespace mozilla {
 namespace dom {
@@ -302,7 +300,6 @@ NS_IMPL_CYCLE_COLLECTING_RELEASE(URLSearchParams)
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(URLSearchParams)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
-  NS_INTERFACE_MAP_ENTRY(nsIXHRSendable)
   NS_INTERFACE_MAP_ENTRY(nsISupports)
 NS_INTERFACE_MAP_END
 
@@ -447,103 +444,5 @@ URLSearchParams::GetValueAtIndex(uint32_t aIndex) const
   return mParams->GetValueAtIndex(aIndex);
 }
 
-// Helper functions for structured cloning
-inline bool
-ReadString(JSStructuredCloneReader* aReader, nsString& aString)
-{
-  MOZ_ASSERT(aReader);
-
-  bool read;
-  uint32_t nameLength, zero;
-  read = JS_ReadUint32Pair(aReader, &nameLength, &zero);
-  if (!read) {
-    return false;
-  }
-  MOZ_ASSERT(zero == 0);
-  aString.SetLength(nameLength);
-  size_t charSize = sizeof(nsString::char_type);
-  read = JS_ReadBytes(aReader, (void*) aString.BeginWriting(),
-                      nameLength * charSize);
-  if (!read) {
-    return false;
-  }
-
-  return true;
-}
-
-inline bool
-WriteString(JSStructuredCloneWriter* aWriter, const nsString& aString)
-{
-  MOZ_ASSERT(aWriter);
-
-  size_t charSize = sizeof(nsString::char_type);
-  return JS_WriteUint32Pair(aWriter, aString.Length(), 0) &&
-         JS_WriteBytes(aWriter, aString.get(), aString.Length() * charSize);
-}
-
-bool
-URLParams::WriteStructuredClone(JSStructuredCloneWriter* aWriter) const
-{
-  const uint32_t& nParams = mParams.Length();
-  if (!JS_WriteUint32Pair(aWriter, nParams, 0)) {
-    return false;
-  }
-  for (uint32_t i = 0; i < nParams; ++i) {
-    if (!WriteString(aWriter, mParams[i].mKey) ||
-        !WriteString(aWriter, mParams[i].mValue)) {
-      return false;
-    }
-  }
-  return true;
-}
-
-bool
-URLParams::ReadStructuredClone(JSStructuredCloneReader* aReader)
-{
-  MOZ_ASSERT(aReader);
-
-  DeleteAll();
-
-  uint32_t nParams, zero;
-  nsAutoString key, value;
-  if (!JS_ReadUint32Pair(aReader, &nParams, &zero)) {
-    return false;
-  }
-  MOZ_ASSERT(zero == 0);
-  for (uint32_t i = 0; i < nParams; ++i) {
-    if (!ReadString(aReader, key) || !ReadString(aReader, value)) {
-      return false;
-    }
-    Append(key, value);
-  }
-  return true;
-}
-
-bool
-URLSearchParams::WriteStructuredClone(JSStructuredCloneWriter* aWriter) const
-{
-  return mParams->WriteStructuredClone(aWriter);
-}
-
-bool
-URLSearchParams::ReadStructuredClone(JSStructuredCloneReader* aReader)
-{
- return mParams->ReadStructuredClone(aReader);
-}
-
-NS_IMETHODIMP
-URLSearchParams::GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
-                             nsACString& aContentType, nsACString& aCharset)
-{
-  aContentType.AssignLiteral("application/x-www-form-urlencoded");
-  aCharset.AssignLiteral("UTF-8");
-
-  nsAutoString serialized;
-  Serialize(serialized);
-  NS_ConvertUTF16toUTF8 converted(serialized);
-  *aContentLength = converted.Length();
-  return NS_NewCStringInputStream(aBody, converted);
-}
-
 } // namespace dom
 } // namespace mozilla
diff --git a/dom/url/URLSearchParams.h b/dom/url/URLSearchParams.h
index 1b81637e08fc..84485b8d875a 100644
--- a/dom/url/URLSearchParams.h
+++ b/dom/url/URLSearchParams.h
@@ -7,14 +7,12 @@
 #ifndef mozilla_dom_URLSearchParams_h
 #define mozilla_dom_URLSearchParams_h
 
-#include "js/StructuredClone.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 #include "nsISupports.h"
 #include "nsIUnicodeDecoder.h"
-#include "nsIXMLHttpRequest.h"
 
 namespace mozilla {
 namespace dom {
@@ -110,12 +108,6 @@ public:
     return mParams[aIndex].mValue;
   }
 
-  bool
-  ReadStructuredClone(JSStructuredCloneReader* aReader);
-
-  bool
-  WriteStructuredClone(JSStructuredCloneWriter* aWriter) const;
-
 private:
   void DecodeString(const nsACString& aInput, nsAString& aOutput);
   void ConvertString(const nsACString& aInput, nsAString& aOutput);
@@ -130,19 +122,17 @@ private:
   nsCOMPtr<nsIUnicodeDecoder> mDecoder;
 };
 
-class URLSearchParams final : public nsIXHRSendable,
+class URLSearchParams final : public nsISupports,
                               public nsWrapperCache
 {
   ~URLSearchParams();
 
 public:
-  NS_DECL_NSIXHRSENDABLE
-
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(URLSearchParams)
 
   URLSearchParams(nsISupports* aParent,
-                  URLSearchParamsObserver* aObserver=nullptr);
+                  URLSearchParamsObserver* aObserver);
 
   URLSearchParams(nsISupports* aParent,
                   const URLSearchParams& aOther);
@@ -199,12 +189,6 @@ public:
     return true;
   }
 
-  bool
-  ReadStructuredClone(JSStructuredCloneReader* aReader);
-
-  bool
-  WriteStructuredClone(JSStructuredCloneWriter* aWriter) const;
-
 private:
   void AppendInternal(const nsAString& aName, const nsAString& aValue);
 
diff --git a/dom/webidl/XMLHttpRequest.webidl b/dom/webidl/XMLHttpRequest.webidl
index 39f527cd6ae7..3dcd004d47e7 100644
--- a/dom/webidl/XMLHttpRequest.webidl
+++ b/dom/webidl/XMLHttpRequest.webidl
@@ -102,8 +102,6 @@ interface XMLHttpRequest : XMLHttpRequestEventTarget {
   void send(FormData data);
   [Throws]
   void send(InputStream data);
-  [Throws]
-  void send(URLSearchParams data);
 
   [Throws]
   void abort();
diff --git a/dom/xhr/XMLHttpRequest.h b/dom/xhr/XMLHttpRequest.h
index 1d4d507cb520..bc5e0785d524 100644
--- a/dom/xhr/XMLHttpRequest.h
+++ b/dom/xhr/XMLHttpRequest.h
@@ -19,7 +19,6 @@ namespace dom {
 
 class Blob;
 class FormData;
-class URLSearchParams;
 class XMLHttpRequestUpload;
 
 class XMLHttpRequest : public XMLHttpRequestEventTarget
@@ -89,9 +88,6 @@ public:
   virtual void
   Send(JSContext* aCx, Blob& aBlob, ErrorResult& aRv) = 0;
 
-  virtual void
-  Send(JSContext* aCx, URLSearchParams& aURLSearchParams, ErrorResult& aRv) = 0;
-
   virtual void
   Send(JSContext* aCx, nsIDocument& aDoc, ErrorResult& aRv) = 0;
 
diff --git a/dom/xhr/XMLHttpRequestMainThread.cpp b/dom/xhr/XMLHttpRequestMainThread.cpp
index 2b67b5222fa8..5a1d8c74e96f 100644
--- a/dom/xhr/XMLHttpRequestMainThread.cpp
+++ b/dom/xhr/XMLHttpRequestMainThread.cpp
@@ -15,7 +15,6 @@
 #include "mozilla/dom/File.h"
 #include "mozilla/dom/FetchUtil.h"
 #include "mozilla/dom/FormData.h"
-#include "mozilla/dom/URLSearchParams.h"
 #include "mozilla/EventDispatcher.h"
 #include "mozilla/EventListenerManager.h"
 #include "mozilla/LoadInfo.h"
@@ -2218,15 +2217,6 @@ GetRequestBodyInternal(nsIInputStream* aStream, nsIInputStream** aResult,
   return NS_OK;
 }
 
-static nsresult
-GetRequestBodyInternal(URLSearchParams* aURLSearchParams,
-                       nsIInputStream** aResult, uint64_t* aContentLength,
-                       nsACString& aContentType, nsACString& aCharset)
-{
-  return aURLSearchParams->GetSendInfo(aResult, aContentLength,
-                                       aContentType, aCharset);
-}
-
 static nsresult
 GetRequestBodyInternal(nsIXHRSendable* aSendable, nsIInputStream** aResult,
                        uint64_t* aContentLength, nsACString& aContentType,
@@ -2407,12 +2397,6 @@ XMLHttpRequestMainThread::GetRequestBody(nsIVariant* aVariant,
       return GetRequestBodyInternal(value.mFormData, aResult, aContentLength,
                                     aContentType, aCharset);
     }
-    case XMLHttpRequestMainThread::RequestBody::eURLSearchParams:
-    {
-      MOZ_ASSERT(value.mURLSearchParams);
-      return GetRequestBodyInternal(value.mURLSearchParams, aResult,
-                                    aContentLength, aContentType, aCharset);
-    }
     case XMLHttpRequestMainThread::RequestBody::eInputStream:
     {
       return GetRequestBodyInternal(value.mStream, aResult, aContentLength,
diff --git a/dom/xhr/XMLHttpRequestMainThread.h b/dom/xhr/XMLHttpRequestMainThread.h
index 724725470edf..90f7b1315c65 100644
--- a/dom/xhr/XMLHttpRequestMainThread.h
+++ b/dom/xhr/XMLHttpRequestMainThread.h
@@ -56,7 +56,6 @@ namespace dom {
 class Blob;
 class BlobSet;
 class FormData;
-class URLSearchParams;
 class XMLHttpRequestUpload;
 
 // A helper for building up an ArrayBuffer object's data
@@ -264,11 +263,6 @@ private:
     {
       mValue.mBlob = &aBlob;
     }
-    explicit RequestBody(mozilla::dom::URLSearchParams& aURLSearchParams) :
-      mType(eURLSearchParams)
-    {
-      mValue.mURLSearchParams = &aURLSearchParams;
-    }
     explicit RequestBody(nsIDocument* aDocument) : mType(eDocument)
     {
       mValue.mDocument = aDocument;
@@ -294,8 +288,7 @@ private:
       eDocument,
       eDOMString,
       eFormData,
-      eInputStream,
-      eURLSearchParams
+      eInputStream
     };
     union Value {
       const ArrayBuffer* mArrayBuffer;
@@ -305,7 +298,6 @@ private:
       const nsAString* mString;
       FormData* mFormData;
       nsIInputStream* mStream;
-      URLSearchParams* mURLSearchParams;
     };
 
     Type GetType() const
@@ -376,12 +368,6 @@ public:
     aRv = Send(RequestBody(aBlob));
   }
 
-  virtual void Send(JSContext* /*aCx*/, URLSearchParams& aURLSearchParams,
-                    ErrorResult& aRv) override
-  {
-    aRv = Send(RequestBody(aURLSearchParams));
-  }
-
   virtual void
   Send(JSContext* /*aCx*/, nsIDocument& aDoc, ErrorResult& aRv) override
   {
diff --git a/dom/xhr/XMLHttpRequestWorker.cpp b/dom/xhr/XMLHttpRequestWorker.cpp
index b09aa14e9d00..093290a67cea 100644
--- a/dom/xhr/XMLHttpRequestWorker.cpp
+++ b/dom/xhr/XMLHttpRequestWorker.cpp
@@ -21,7 +21,6 @@
 #include "mozilla/dom/FormData.h"
 #include "mozilla/dom/ProgressEvent.h"
 #include "mozilla/dom/StructuredCloneHolder.h"
-#include "mozilla/dom/URLSearchParams.h"
 #include "mozilla/Telemetry.h"
 #include "nsComponentManagerUtils.h"
 #include "nsContentUtils.h"
@@ -2167,39 +2166,6 @@ XMLHttpRequestWorker::Send(JSContext* aCx, FormData& aBody, ErrorResult& aRv)
   SendInternal(sendRunnable, aRv);
 }
 
-void
-XMLHttpRequestWorker::Send(JSContext* aCx, URLSearchParams& aBody,
-                           ErrorResult& aRv)
-{
-  mWorkerPrivate->AssertIsOnWorkerThread();
-
-  if (mCanceled) {
-    aRv.ThrowUncatchableException();
-    return;
-  }
-
-  if (!mProxy) {
-    aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
-    return;
-  }
-
-  JS::Rooted<JS::Value> value(aCx);
-  if (!GetOrCreateDOMReflector(aCx, &aBody, &value)) {
-    aRv.Throw(NS_ERROR_FAILURE);
-    return;
-  }
-
-  RefPtr<SendRunnable> sendRunnable =
-    new SendRunnable(mWorkerPrivate, mProxy, EmptyString());
-
-  sendRunnable->Write(aCx, value, aRv);
-  if (NS_WARN_IF(aRv.Failed())) {
-    return;
-  }
-
-  SendInternal(sendRunnable, aRv);
-}
-
 void
 XMLHttpRequestWorker::Send(JSContext* aCx, const ArrayBuffer& aBody,
                            ErrorResult& aRv)
diff --git a/dom/xhr/XMLHttpRequestWorker.h b/dom/xhr/XMLHttpRequestWorker.h
index f924554733b6..6edbc084de6c 100644
--- a/dom/xhr/XMLHttpRequestWorker.h
+++ b/dom/xhr/XMLHttpRequestWorker.h
@@ -175,9 +175,6 @@ public:
   virtual void
   Send(JSContext* aCx, const ArrayBufferView& aBody, ErrorResult& aRv) override;
 
-  virtual void
-  Send(JSContext* aCx, URLSearchParams& aBody, ErrorResult& aRv) override;
-
   virtual void
   Send(JSContext* aCx, nsIDocument& aDoc, ErrorResult& aRv) override
   {
diff --git a/testing/web-platform/meta/XMLHttpRequest/setrequestheader-content-type.htm.ini b/testing/web-platform/meta/XMLHttpRequest/setrequestheader-content-type.htm.ini
deleted file mode 100644
index 6e9ca775ee21..000000000000
--- a/testing/web-platform/meta/XMLHttpRequest/setrequestheader-content-type.htm.ini
+++ /dev/null
@@ -1,10 +0,0 @@
-[setrequestheader-content-type.htm]
-  type: testharness
-  [ReadableStream request respects setRequestHeader("")]
-    expected: FAIL
-
-  [ReadableStream request with under type sends no Content-Type without setRequestHeader() call]
-    expected: FAIL
-
-  [ReadableStream request keeps setRequestHeader() Content-Type and charset]
-    expected: FAIL
diff --git a/testing/web-platform/tests/XMLHttpRequest/setrequestheader-content-type.htm b/testing/web-platform/tests/XMLHttpRequest/setrequestheader-content-type.htm
index 64a72927a6dd..a648efa64ca6 100644
--- a/testing/web-platform/tests/XMLHttpRequest/setrequestheader-content-type.htm
+++ b/testing/web-platform/tests/XMLHttpRequest/setrequestheader-content-type.htm
@@ -9,229 +9,19 @@
   <body>
     <div id="log"></div>
     <script>
-      function request(inputGenerator, headersToSend, expectedType, title) {
+      function request(value) {
         test(function() {
-          try {
-            var toSend = inputGenerator();
-          } catch(e) {
-            assert_unreached("Skipping test as could not create a " + inputGenerator.name.replace("_", "") + "; ");
-          }
           var client = new XMLHttpRequest()
           client.open("POST", "resources/inspect-headers.py?filter_name=Content-Type", false)
-          for(header in headersToSend) {
-            if (headersToSend.hasOwnProperty(header)) {
-              client.setRequestHeader(header, headersToSend[header]);
-            }
-          }
-          client.send(toSend)
-
-          var responseType = client.responseText.replace("\n", "").replace("; ", ";").toLowerCase(); // don't care about case or space after semicolon for charset
-          if (expectedType === undefined || expectedType === null) {
-            assert_equals(responseType, "");
-          } else if (expectedType instanceof RegExp) {
-            if (!expectedType.ignoreCase) expectedType = new RegExp(expectedType, "i"); // always ignore case; the regex itself will have to remember to handle the optional space after the semicolon for charset
-            assert_regexp_match(responseType, expectedType);
-          } else {
-            expectedType = "content-type: " + String(expectedType ? expectedType.trim().replace("; ", ";") : expectedType).toLowerCase()
-            assert_equals(responseType, expectedType);
-          }
-        }, title)
+          client.setRequestHeader('Content-Type', value)
+          client.send("")
+          assert_equals(client.responseText, 'content-type: '+ String(value ? value.trim() : value).toLowerCase()+'\n' )
+        }, document.title + " (" + value + ")")
       }
-      request(
-        function _String() { return ""; },
-        {"Content-Type": ""},
-        "",
-        'setRequestHeader("") sends a blank string'
-      )
-      request(
-        function _String() { return ""; },
-        {"Content-Type": " "},
-        " ",
-        'setRequestHeader(" ") sends the string " "'
-      )
-      request(
-        function _String() { return ""; },
-        {"Content-Type": null},
-        "null",
-        'setRequestHeader(null) sends the string "null"'
-      )
-      request(
-        function _String() { return ""; },
-        {"Content-Type": undefined},
-        "undefined",
-        'setRequestHeader(undefined) sends the string "undefined"'
-      )
-      request(
-        function _String() { return "test"; },
-        {},
-        "text/plain;charset=UTF-8",
-        'String request has correct default Content-Type of "text/plain;charset=UTF-8"'
-      )
-      request(
-        function _String() { return "test()"; },
-        {"Content-Type": "text/javascript;charset=ASCII"},
-        "text/javascript;charset=UTF-8",
-        "String request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8"
-      )
-      request(
-        function _XMLDocument() { return new DOMParser().parseFromString("<xml/>", "application/xml"); },
-        {"Content-Type": ""},
-        "",
-        'XML Document request respects setRequestHeader("")'
-      )
-      request(
-        function _XMLDocument() { return new DOMParser().parseFromString("<xml/>", "application/xml"); },
-        {},
-        "application/xml;charset=UTF-8",
-        'XML Document request has correct default Content-Type of "application/xml;charset=UTF-8"'
-      )
-      request(
-        function _XMLDocument() { return new DOMParser().parseFromString("<xml/>", "application/xml"); },
-        {"Content-Type": "application/xhtml+xml;charset=ASCII"},
-        "application/xhtml+xml;charset=UTF-8",
-        "XML Document request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8"
-      )
-      request(
-        function _HTMLDocument() { return new DOMParser().parseFromString("<html></html>", "text/html"); },
-        {"Content-Type": ""},
-        "",
-        'HTML Document request respects setRequestHeader("")'
-      )
-      request(
-        function _HTMLDocument() { return new DOMParser().parseFromString("<html></html>", "text/html"); },
-        {},
-        "text/html;charset=UTF-8",
-        'HTML Document request has correct default Content-Type of "text/html;charset=UTF-8"'
-      )
-      request(
-        function _HTMLDocument() { return new DOMParser().parseFromString("<html></html>", "text/html"); },
-        {"Content-Type": "text/html+junk;charset=ASCII"},
-        "text/html+junk;charset=UTF-8",
-        "HTML Document request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8"
-      )
-      request(
-        function _Blob() { return new Blob(["test"]); },
-        {"Content-Type": ""},
-        "",
-        'Blob request respects setRequestHeader("") to be specified'
-      )
-      request(
-        function _Blob() { return new Blob(["test"]); },
-        {},
-        undefined,
-        "Blob request with unset type sends no Content-Type without setRequestHeader() call"
-      )
-      request(
-        function _Blob() { return new Blob(["test"]); },
-        {"Content-Type": "application/xml;charset=ASCII"},
-        "application/xml;charset=ASCII",
-        "Blob request with unset type keeps setRequestHeader() Content-Type and charset"
-      )
-      request(
-        function _Blob() { return new Blob(["<xml/>"], {type : "application/xml;charset=ASCII"}); },
-        {},
-        "application/xml;charset=ASCII",
-        "Blob request with set type uses that it for Content-Type unless setRequestHeader()"
-      )
-      request(
-        function _Blob() { return new Blob(["<xml/>"], {type : "application/xml;charset=UTF8"}); },
-        {"Content-Type": "application/xml+junk;charset=ASCII"},
-        "application/xml+junk;charset=ASCII",
-        "Blob request with set type keeps setRequestHeader() Content-Type and charset"
-      )
-      request(
-        function _ArrayBuffer() { return new ArrayBuffer(10); },
-        {"Content-Type": ""},
-        "",
-        'ArrayBuffer request respects setRequestHeader("")'
-      )
-      request(
-        function _ArrayBuffer() { return new ArrayBuffer(10); },
-        {},
-        undefined,
-        "ArrayBuffer request sends no Content-Type without setRequestHeader() call"
-      )
-      request(
-        function _ArrayBuffer() { return new ArrayBuffer(10); },
-        {"Content-Type": "application/xml;charset=ASCII"},
-        "application/xml;charset=ASCII",
-        "ArrayBuffer request keeps setRequestHeader() Content-Type and charset"
-      )
-      request(
-        function _Uint8Array() { return new Uint8Array(new ArrayBuffer(10)); },
-        {"Content-Type": ""},
-        "",
-        'ArrayBufferView request respects setRequestHeader("")'
-      )
-      request(
-        function _Uint8Array() { return new Uint8Array(new ArrayBuffer(10)); },
-        {},
-        undefined,
-        "ArrayBufferView request sends no Content-Type without setRequestHeader() call"
-      )
-      request(
-        function _Uint8Array() { return new Uint8Array(new ArrayBuffer(10)); },
-        {"Content-Type": "application/xml;charset=ASCII"},
-        "application/xml;charset=ASCII",
-        "ArrayBufferView request keeps setRequestHeader() Content-Type and charset"
-      )
-      request(
-        function _FormData() { return new FormData(); },
-        {"Content-Type": ""},
-        "",
-        'FormData request respects setRequestHeader("")'
-      )
-      request(
-        function _FormData() { return new FormData(); },
-        {},
-        /multipart\/form-data;boundary=(.*)/,
-        'FormData request has correct default Content-Type of "multipart\/form-data;boundary=_"'
-      )
-      request(
-        function _FormData() { return new FormData(); },
-        {"Content-Type": "application/xml;charset=ASCII"},
-        "application/xml;charset=ASCII",
-        "FormData request keeps setRequestHeader() Content-Type and charset"
-      )
-      request(
-        function _URLSearchParams() { return new URLSearchParams("q=testQ&topic=testTopic") },
-        {"Content-Type": ""},
-        "",
-        'URLSearchParams respects setRequestHeader("")'
-      )
-      request(
-        function _URLSearchParams() { return new URLSearchParams("q=testQ&topic=testTopic") },
-        {},
-        "application/x-www-form-urlencoded;charset=UTF-8",
-        'URLSearchParams request has correct default Content-Type of "application/x-www-form-urlencoded;charset=UTF-8"'
-      )
-      request(
-        function _URLSearchParams() { return new URLSearchParams("q=testQ&topic=testTopic") },
-        {"Content-Type": "application/xml;charset=ASCII"},
-        "application/xml;charset=UTF-8",
-        "URLSearchParams request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8"
-        // the default Content-Type for URLSearchParams has a charset specified (utf-8) in
-        // https://fetch.spec.whatwg.org/#bodyinit, so the user's must be changed to match it
-        // as per https://xhr.spec.whatwg.org/#the-send%28%29-method step 4.
-      )
-      request(
-        function _ReadableStream() { return new ReadableStream() },
-        {"Content-Type": ""},
-        "",
-        'ReadableStream request respects setRequestHeader("")'
-      )
-      request(
-        function _ReadableStream() { return new ReadableStream() },
-        {},
-        undefined,
-        "ReadableStream request with under type sends no Content-Type without setRequestHeader() call"
-      )
-      request(
-        function _ReadableStream() { return new ReadableStream() },
-        {"Content-Type": "application/xml;charset=ASCII"},
-        "application/xml;charset=ASCII",
-        "ReadableStream request keeps setRequestHeader() Content-Type and charset"
-      )
+      request("")
+      request(" ")
+      request(null)
+      request(undefined)
     </script>
   </body>
 </html>
diff --git a/toolkit/components/places/tests/cpp/mock_Link.h b/toolkit/components/places/tests/cpp/mock_Link.h
index 8e1cb91c9344..7d2ec50a39d9 100644
--- a/toolkit/components/places/tests/cpp/mock_Link.h
+++ b/toolkit/components/places/tests/cpp/mock_Link.h
@@ -215,14 +215,6 @@ URLSearchParams::NotifyObserver()
   NS_NOTREACHED("Unexpected call to URLSearchParams::NotifyObserver");
 }
 
-NS_IMETHODIMP
-URLSearchParams::GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
-                             nsACString& aContentType, nsACString& aCharset)
-{
-  NS_NOTREACHED("Unexpected call to URLSearchParams::GetSendInfo");
-  return NS_OK;
-}
-
 } // namespace dom
 } // namespace mozilla