Bug 1504344 - Remove the pref dom.xhr.lowercase_header.enabled; r=baku

Remove the pref dom.xhr.lowercase_header.enabled, as we are unaware of any actionable compat concerns now that bug 1540688 landed, and an ESR had been spun off.

Differential Revision: https://phabricator.services.mozilla.com/D39636

--HG--
extra : moz-landing-system : lando

dom/xhr/XMLHttpRequestMainThread.cpp

@@ -2969,20 +2969,6 @@ bool XMLHttpRequestMainThread::IsMappedArrayBufferEnabled() {
   return sIsMappedArrayBufferEnabled;
 }
 
-/* static */
-bool XMLHttpRequestMainThread::IsLowercaseResponseHeader() {
-  static bool sLowercaseResponseHeaderAdded = false;
-  static bool sIsLowercaseResponseHeaderEnabled;
-
-  if (!sLowercaseResponseHeaderAdded) {
-    Preferences::AddBoolVarCache(&sIsLowercaseResponseHeaderEnabled,
-                                 "dom.xhr.lowercase_header.enabled", false);
-    sLowercaseResponseHeaderAdded = true;
-  }
-
-  return sIsLowercaseResponseHeaderEnabled;
-}
-
 // http://dvcs.w3.org/hg/xhr/raw-file/tip/Overview.html#dom-xmlhttprequest-setrequestheader
 void XMLHttpRequestMainThread::SetRequestHeader(const nsACString& aName,
                                                 const nsACString& aValue,
@@ -3572,14 +3558,6 @@ NS_IMPL_ISUPPORTS(XMLHttpRequestMainThread::nsHeaderVisitor,
 NS_IMETHODIMP XMLHttpRequestMainThread::nsHeaderVisitor::VisitHeader(
     const nsACString& header, const nsACString& value) {
   if (mXHR.IsSafeHeader(header, mHttpChannel)) {
-    if (!IsLowercaseResponseHeader()) {
-      if (!mHeaderList.InsertElementSorted(HeaderEntry(header, value),
-                                           fallible)) {
-        return NS_ERROR_OUT_OF_MEMORY;
-      }
-      return NS_OK;
-    }
-
     nsAutoCString lowerHeader(header);
     ToLowerCase(lowerHeader);
     if (!mHeaderList.InsertElementSorted(HeaderEntry(lowerHeader, value),

dom/xhr/XMLHttpRequestMainThread.h

@@ -304,10 +304,6 @@ class XMLHttpRequestMainThread final : public XMLHttpRequest,
   // supported.
   static bool IsMappedArrayBufferEnabled();
 
-  // Check pref "dom.xhr.lowercase_header.enabled" to make sure lowercased
-  // response header is supported.
-  static bool IsLowercaseResponseHeader();
-
   void MaybeLowerChannelPriority();
 
  public:
@@ -526,9 +522,6 @@ class XMLHttpRequestMainThread final : public XMLHttpRequest,
       }
 
       bool operator<(const HeaderEntry& aOther) const {
-        if (!IsLowercaseResponseHeader()) {
-          return mName < aOther.mName;
-        }
         uint32_t selfLen = mName.Length();
         uint32_t otherLen = aOther.mName.Length();
         uint32_t min = XPCOM_MIN(selfLen, otherLen);

modules/libpref/init/all.js

@@ -5453,9 +5453,6 @@ pref("toolkit.telemetry.overrideUpdateChannel", "nightly-asan");
 pref("layers.mlgpu.enable-on-windows7", true);
 #endif
 
-// Enable lowercased response header name
-pref("dom.xhr.lowercase_header.enabled", true);
-
 // Control whether clients.openWindow() opens windows in the same process
 // that called the API vs following our normal multi-process selection
 // algorithm.  Restricting openWindow to same process improves service worker

testing/web-platform/meta/xhr/__dir__.ini

@@ -1 +1 @@
-prefs: [dom.xhr.lowercase_header.enabled:true, javascript.options.streams:true, dom.xhr.standard_content_type_normalization:true]
+prefs: [javascript.options.streams:true, dom.xhr.standard_content_type_normalization:true]