1 files changed, 93 insertions, 0 deletions
diff --git a/layout/style/PreloadedStyleSheet.cpp b/layout/style/PreloadedStyleSheet.cpp
new file mode 100644
index 0000000000..6f5896933e
--- /dev/null
+++ b/layout/style/PreloadedStyleSheet.cpp
@@ -0,0 +1,93 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/* a CSS style sheet returned from nsIStyleSheetService.preloadSheet */
+
+#include "PreloadedStyleSheet.h"
+
+#include "mozilla/css/Loader.h"
+#include "mozilla/dom/Promise.h"
+#include "nsICSSLoaderObserver.h"
+#include "nsLayoutUtils.h"
+
+namespace mozilla {
+
+PreloadedStyleSheet::PreloadedStyleSheet(nsIURI* aURI,
+                                         css::SheetParsingMode aParsingMode)
+    : mLoaded(false), mURI(aURI), mParsingMode(aParsingMode) {}
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(PreloadedStyleSheet)
+  NS_INTERFACE_MAP_ENTRY(nsIPreloadedStyleSheet)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(PreloadedStyleSheet)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(PreloadedStyleSheet)
+
+NS_IMPL_CYCLE_COLLECTION(PreloadedStyleSheet, mSheet)
+
+nsresult PreloadedStyleSheet::GetSheet(StyleSheet** aResult) {
+  *aResult = nullptr;
+
+  MOZ_DIAGNOSTIC_ASSERT(mLoaded);
+
+  if (!mSheet) {
+    RefPtr<css::Loader> loader = new css::Loader;
+    auto result = loader->LoadSheetSync(mURI, mParsingMode,
+                                        css::Loader::UseSystemPrincipal::Yes);
+    if (result.isErr()) {
+      return result.unwrapErr();
+    }
+    mSheet = result.unwrap();
+  }
+
+  *aResult = mSheet;
+  return NS_OK;
+}
+
+nsresult PreloadedStyleSheet::Preload() {
+  MOZ_DIAGNOSTIC_ASSERT(!mLoaded);
+  mLoaded = true;
+  StyleSheet* sheet;
+  return GetSheet(&sheet);
+}
+
+NS_IMPL_ISUPPORTS(PreloadedStyleSheet::StylesheetPreloadObserver,
+                  nsICSSLoaderObserver)
+
+NS_IMETHODIMP
+PreloadedStyleSheet::StylesheetPreloadObserver::StyleSheetLoaded(
+    StyleSheet* aSheet, bool aWasDeferred, nsresult aStatus) {
+  MOZ_DIAGNOSTIC_ASSERT(!mPreloadedSheet->mLoaded);
+  mPreloadedSheet->mLoaded = true;
+
+  if (NS_FAILED(aStatus)) {
+    mPromise->MaybeReject(aStatus);
+  } else {
+    mPromise->MaybeResolve(mPreloadedSheet);
+  }
+
+  return NS_OK;
+}
+
+// Note: After calling this method, the preloaded sheet *must not* be used
+// until the observer is notified that the sheet has finished loading.
+nsresult PreloadedStyleSheet::PreloadAsync(NotNull<dom::Promise*> aPromise) {
+  MOZ_DIAGNOSTIC_ASSERT(!mLoaded);
+
+  RefPtr<css::Loader> loader = new css::Loader;
+  RefPtr<StylesheetPreloadObserver> obs =
+      new StylesheetPreloadObserver(aPromise, this);
+  auto result = loader->LoadSheet(mURI, mParsingMode,
+                                  css::Loader::UseSystemPrincipal::No, obs);
+  if (result.isErr()) {
+    return result.unwrapErr();
+  }
+  mSheet = result.unwrap();
+  return NS_OK;
+}
+
+}  // namespace mozilla