1 files changed, 21 insertions, 26 deletions

diff --git a/layout/style/StyleSheet.cpp b/layout/style/StyleSheet.cpp
index 494618d879..b1ce1d66e2 100644
--- a/layout/style/StyleSheet.cpp
+++ b/layout/style/StyleSheet.cpp
@@ -28,7 +28,6 @@
 #include "mozilla/css/SheetLoadData.h"
 
 #include "mozAutoDocUpdate.h"
-#include "SheetLoadData.h"
 
 namespace mozilla {
 
@@ -136,8 +135,12 @@ already_AddRefed<StyleSheet> StyleSheet::Constructor(
 
   // 3. Set the sheet's disabled flag according to aOptions.
   sheet->SetDisabled(aOptions.mDisabled);
+  sheet->SetURLExtraData();
   sheet->SetComplete();
 
+  sheet->ReplaceSync(""_ns, aRv);
+  MOZ_ASSERT(!aRv.Failed());
+
   // 4. Return sheet.
   return sheet.forget();
 }
@@ -740,7 +743,9 @@ already_AddRefed<dom::Promise> StyleSheet::Replace(const nsACString& aText,
   loadData->mIsBeingParsed = true;
   MOZ_ASSERT(!mReplacePromise);
   mReplacePromise = promise;
-  ParseSheet(*loader, aText, *loadData)
+  RefPtr<css::SheetLoadDataHolder> holder(
+      new css::SheetLoadDataHolder(__func__, loadData, false));
+  ParseSheet(*loader, aText, holder)
       ->Then(
           target, __func__,
           [loadData] { loadData->SheetFinishedParsingAsync(); },
@@ -769,7 +774,6 @@ void StyleSheet::ReplaceSync(const nsACString& aText, ErrorResult& aRv) {
   // 3. Parse aText into rules.
   // 4. If rules contain @imports, skip them and continue parsing.
   auto* loader = mConstructorDocument->CSSLoader();
-  SetURLExtraData();
   RefPtr<const StyleStylesheetContents> rawContent =
       Servo_StyleSheet_FromUTF8Bytes(
           loader, this,
@@ -1159,28 +1163,19 @@ already_AddRefed<StyleSheet> StyleSheet::CreateEmptyChildSheet(
   return child.forget();
 }
 
-// We disable parallel stylesheet parsing if the browser is recording CSS errors
-// (which parallel parsing can't handle).
-static bool AllowParallelParse(css::Loader& aLoader, URLExtraData* aUrlData) {
-  Document* doc = aLoader.GetDocument();
-  if (doc && css::ErrorReporter::ShouldReportErrors(*doc)) {
-    return false;
-  }
-  // Otherwise we can parse in parallel.
-  return true;
-}
-
 RefPtr<StyleSheetParsePromise> StyleSheet::ParseSheet(
     css::Loader& aLoader, const nsACString& aBytes,
-    css::SheetLoadData& aLoadData) {
+    const RefPtr<css::SheetLoadDataHolder>& aLoadData) {
   MOZ_ASSERT(mParsePromise.IsEmpty());
+  MOZ_ASSERT_IF(NS_IsMainThread(), mAsyncParseBlockers == 0);
+
   RefPtr<StyleSheetParsePromise> p = mParsePromise.Ensure(__func__);
-  if (!aLoadData.ShouldDefer()) {
+  if (!aLoadData->get()->ShouldDefer()) {
     mParsePromise.SetTaskPriority(nsIRunnablePriority::PRIORITY_RENDER_BLOCKING,
                                   __func__);
   }
+  BlockParsePromise();
   SetURLExtraData();
-
   // @import rules are disallowed due to this decision:
   // https://github.com/WICG/construct-stylesheets/issues/119#issuecomment-588352418
   // We may allow @import rules again in the future.
@@ -1191,26 +1186,26 @@ RefPtr<StyleSheetParsePromise> StyleSheet::ParseSheet(
   const bool shouldRecordCounters =
       aLoader.GetDocument() && aLoader.GetDocument()->GetStyleUseCounters() &&
       !urlData->ChromeRulesEnabled();
-  if (!AllowParallelParse(aLoader, urlData)) {
+
+  if (aLoadData->get()->mRecordErrors) {
+    MOZ_ASSERT(NS_IsMainThread());
     UniquePtr<StyleUseCounters> counters;
     if (shouldRecordCounters) {
       counters.reset(Servo_UseCounters_Create());
     }
-
     RefPtr<StyleStylesheetContents> contents =
         Servo_StyleSheet_FromUTF8Bytes(
-            &aLoader, this, &aLoadData, &aBytes, mParsingMode, urlData,
-            aLoadData.mCompatMode,
+            &aLoader, this, aLoadData->get(), &aBytes, mParsingMode, urlData,
+            aLoadData->get()->mCompatMode,
             /* reusable_sheets = */ nullptr, counters.get(), allowImportRules,
             StyleSanitizationKind::None,
             /* sanitized_output = */ nullptr)
             .Consume();
     FinishAsyncParse(contents.forget(), std::move(counters));
   } else {
-    auto holder = MakeRefPtr<css::SheetLoadDataHolder>(__func__, &aLoadData);
-    Servo_StyleSheet_FromUTF8BytesAsync(holder, urlData, &aBytes, mParsingMode,
-                                        aLoadData.mCompatMode,
-                                        shouldRecordCounters, allowImportRules);
+    Servo_StyleSheet_FromUTF8BytesAsync(
+        aLoadData, urlData, &aBytes, mParsingMode,
+        aLoadData->get()->mCompatMode, shouldRecordCounters, allowImportRules);
   }
 
   return p;
@@ -1224,7 +1219,7 @@ void StyleSheet::FinishAsyncParse(
   Inner().mContents = aSheetContents;
   Inner().mUseCounters = std::move(aUseCounters);
   FixUpRuleListAfterContentsChangeIfNeeded();
-  mParsePromise.Resolve(true, __func__);
+  UnblockParsePromise();
 }
 
 void StyleSheet::ParseSheetSync(