--- a/layout/style/Loader.cpp
+++ b/layout/style/Loader.cpp
@@ -11,16 +11,17 @@
 
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/dom/DocGroup.h"
 #include "mozilla/IntegerPrintfMacros.h"
 #include "mozilla/LoadInfo.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/StyleSheetInlines.h"
 #include "mozilla/SystemGroup.h"
+#include "mozilla/URLPreloader.h"
 #include "nsIRunnable.h"
 #include "nsIUnicharStreamLoader.h"
 #include "nsSyncLoadService.h"
 #include "nsCOMPtr.h"
 #include "nsString.h"
 #include "nsIContent.h"
 #include "nsIDocument.h"
 #include "nsIDOMNode.h"
@@ -39,16 +40,17 @@
 #include "nsIStyleSheetLinkingElement.h"
 #include "nsICSSLoaderObserver.h"
 #include "nsCSSParser.h"
 #include "mozilla/css/ImportRule.h"
 #include "nsThreadUtils.h"
 #include "nsGkAtoms.h"
 #include "nsIThreadInternal.h"
 #include "nsINetworkPredictor.h"
+#include "nsStringStream.h"
 #include "mozilla/dom/MediaList.h"
 #include "mozilla/dom/ShadowRoot.h"
 #include "mozilla/dom/URL.h"
 #include "mozilla/AsyncEventDispatcher.h"
 #include "mozilla/ServoBindings.h"
 #include "mozilla/StyleSheet.h"
 #include "mozilla/StyleSheetInlines.h"
 #include "mozilla/ConsoleReportCollector.h"
@@ -1506,21 +1508,35 @@ Loader::LoadSheet(SheetLoadData* aLoadDa
                                                 securityFlags,
                                                 contentPolicyType);
     }
     else {
       // either we are loading something inside a document, in which case
       // we should always have a requestingNode, or we are loading something
       // outside a document, in which case the loadingPrincipal and the
       // triggeringPrincipal should always be the systemPrincipal.
-      rv = NS_NewChannel(getter_AddRefs(channel),
-                         aLoadData->mURI,
-                         nsContentUtils::GetSystemPrincipal(),
-                         securityFlags,
-                         contentPolicyType);
+      auto result = URLPreloader::ReadURI(aLoadData->mURI);
+      if (result.isOk()) {
+        nsCOMPtr<nsIInputStream> stream;
+        rv = NS_NewCStringInputStream(getter_AddRefs(stream), result.unwrap());
+        NS_ENSURE_SUCCESS(rv, rv);
+
+        rv = NS_NewInputStreamChannel(getter_AddRefs(channel),
+                                      aLoadData->mURI,
+                                      stream,
+                                      nsContentUtils::GetSystemPrincipal(),
+                                      securityFlags,
+                                      contentPolicyType);
+      } else {
+        rv = NS_NewChannel(getter_AddRefs(channel),
+                           aLoadData->mURI,
+                           nsContentUtils::GetSystemPrincipal(),
+                           securityFlags,
+                           contentPolicyType);
+      }
     }
     if (NS_FAILED(rv)) {
       LOG_ERROR(("  Failed to create channel"));
       SheetComplete(aLoadData, rv);
       return rv;
     }
 
     nsCOMPtr<nsIInputStream> stream;