From 2aa4a82499d4becd2284cdb482213d541b8804dd Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 28 Apr 2024 16:29:10 +0200
Subject: Adding upstream version 86.0.1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 layout/base/nsPresContext.cpp | 2961 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 2961 insertions(+)
 create mode 100644 layout/base/nsPresContext.cpp

(limited to 'layout/base/nsPresContext.cpp')

diff --git a/layout/base/nsPresContext.cpp b/layout/base/nsPresContext.cpp
new file mode 100644
index 0000000000..c7eabb2486
--- /dev/null
+++ b/layout/base/nsPresContext.cpp
@@ -0,0 +1,2961 @@
+/* -*- 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 presentation of a document, part 1 */
+
+#include "nsPresContext.h"
+#include "nsPresContextInlines.h"
+
+#include "mozilla/ArrayUtils.h"
+#if defined(MOZ_WIDGET_ANDROID)
+#  include "mozilla/AsyncEventDispatcher.h"
+#endif
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Encoding.h"
+#include "mozilla/EventDispatcher.h"
+#include "mozilla/EventStateManager.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/PresShellInlines.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/WindowGlobalChild.h"
+
+#include "base/basictypes.h"
+
+#include "nsCOMPtr.h"
+#include "nsCSSFrameConstructor.h"
+#include "nsDocShell.h"
+#include "nsIContentViewer.h"
+#include "nsPIDOMWindow.h"
+#include "mozilla/ServoStyleSet.h"
+#include "mozilla/MediaFeatureChange.h"
+#include "nsIContent.h"
+#include "nsIFrame.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/DocumentInlines.h"
+#include "nsIPrintSettings.h"
+#include "nsLanguageAtomService.h"
+#include "mozilla/LookAndFeel.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsHTMLDocument.h"
+#include "nsIWeakReferenceUtils.h"
+#include "nsThreadUtils.h"
+#include "nsLayoutUtils.h"
+#include "nsViewManager.h"
+#include "mozilla/RestyleManager.h"
+#include "SurfaceCacheUtils.h"
+#include "nsMediaFeatures.h"
+#include "gfxPlatform.h"
+#include "nsFontFaceLoader.h"
+#include "mozilla/AnimationEventDispatcher.h"
+#include "mozilla/EffectCompositor.h"
+#include "mozilla/EventListenerManager.h"
+#include "prenv.h"
+#include "nsPluginFrame.h"
+#include "nsTransitionManager.h"
+#include "nsAnimationManager.h"
+#include "CounterStyleManager.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/dom/Element.h"
+#include "nsIMessageManager.h"
+#include "mozilla/dom/HTMLBodyElement.h"
+#include "mozilla/dom/MediaQueryList.h"
+#include "mozilla/SMILAnimationController.h"
+#include "mozilla/css/ImageLoader.h"
+#include "mozilla/dom/PBrowserParent.h"
+#include "mozilla/dom/BrowserChild.h"
+#include "mozilla/dom/BrowserParent.h"
+#include "mozilla/StaticPresData.h"
+#include "nsRefreshDriver.h"
+#include "Layers.h"
+#include "LayerUserData.h"
+#include "ClientLayerManager.h"
+#include "mozilla/dom/NotifyPaintEvent.h"
+
+#include "nsFrameLoader.h"
+#include "nsContentUtils.h"
+#include "nsPIWindowRoot.h"
+#include "mozilla/Preferences.h"
+#include "gfxTextRun.h"
+#include "nsFontFaceUtils.h"
+#include "mozilla/GlobalStyleSheetCache.h"
+#include "mozilla/ServoBindings.h"
+#include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/StaticPrefs_zoom.h"
+#include "mozilla/StyleSheet.h"
+#include "mozilla/StyleSheetInlines.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/dom/Performance.h"
+#include "mozilla/dom/PerformanceTiming.h"
+#include "mozilla/dom/PerformancePaintTiming.h"
+#include "mozilla/layers/APZThreadUtils.h"
+#include "MobileViewportManager.h"
+#include "mozilla/dom/ImageTracker.h"
+
+// Needed for Start/Stop of Image Animation
+#include "imgIContainer.h"
+#include "nsIImageLoadingContent.h"
+
+#include "nsBidiUtils.h"
+#include "nsServiceManagerUtils.h"
+#include "nsBidi.h"
+
+#include "mozilla/dom/URL.h"
+#include "mozilla/ServoCSSParser.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::gfx;
+using namespace mozilla::layers;
+
+uint8_t gNotifySubDocInvalidationData;
+
+/**
+ * Layer UserData for ContainerLayers that want to be notified
+ * of local invalidations of them and their descendant layers.
+ * Pass a callback to ComputeDifferences to have these called.
+ */
+class ContainerLayerPresContext : public LayerUserData {
+ public:
+  nsPresContext* mPresContext;
+};
+
+bool nsPresContext::IsDOMPaintEventPending() {
+  if (!mTransactions.IsEmpty()) {
+    return true;
+  }
+
+  nsRootPresContext* drpc = GetRootPresContext();
+  if (drpc && drpc->mRefreshDriver->ViewManagerFlushIsPending()) {
+    // Since we're promising that there will be a MozAfterPaint event
+    // fired, we record an empty invalidation in case display list
+    // invalidation doesn't invalidate anything further.
+    NotifyInvalidation(drpc->mRefreshDriver->LastTransactionId().Next(),
+                       nsRect(0, 0, 0, 0));
+    return true;
+  }
+  return false;
+}
+
+void nsPresContext::ForceReflowForFontInfoUpdate() {
+  // Flush the device context's font cache, so that we won't risk getting
+  // stale nsFontMetrics objects from it.
+  DeviceContext()->FlushFontCache();
+
+  // If there's a user font set, discard any src:local() faces it may have
+  // loaded because their font entries may no longer be valid.
+  if (Document()->GetFonts()) {
+    Document()->GetFonts()->GetUserFontSet()->ForgetLocalFaces();
+  }
+
+  // We can trigger reflow by pretending a font.* preference has changed;
+  // this is the same mechanism as gfxPlatform::ForceGlobalReflow() uses
+  // if new fonts are installed during the session, for example.
+  PreferenceChanged("font.internaluseonly.changed");
+}
+
+static bool IsVisualCharset(NotNull<const Encoding*> aCharset) {
+  return aCharset == ISO_8859_8_ENCODING;
+}
+
+nsPresContext::nsPresContext(dom::Document* aDocument, nsPresContextType aType)
+    : mPresShell(nullptr),
+      mDocument(aDocument),
+      mMedium(aType == eContext_Galley ? nsGkAtoms::screen : nsGkAtoms::print),
+      mSystemFontScale(1.0),
+      mTextZoom(1.0),
+      mEffectiveTextZoom(1.0),
+      mFullZoom(1.0),
+      mLastFontInflationScreenSize(gfxSize(-1.0, -1.0)),
+      mCurAppUnitsPerDevPixel(0),
+      mAutoQualityMinFontSizePixelsPref(0),
+      mDynamicToolbarMaxHeight(0),
+      mDynamicToolbarHeight(0),
+      mPageSize(-1, -1),
+      mPageScale(0.0),
+      mPPScale(1.0f),
+      mViewportScrollOverrideElement(nullptr),
+      mElementsRestyled(0),
+      mFramesConstructed(0),
+      mFramesReflowed(0),
+      mChangeHintForPrefChange(nsChangeHint(0)),
+      mInterruptChecksToSkip(0),
+      mNextFrameRateMultiplier(0),
+      mViewportScrollStyles(StyleOverflow::Auto, StyleOverflow::Auto),
+      // mImageAnimationMode is initialised below, in constructor body
+      mImageAnimationModePref(imgIContainer::kNormalAnimMode),
+      mType(aType),
+      mInflationDisabledForShrinkWrap(false),
+      mInteractionTimeEnabled(true),
+      mHasPendingInterrupt(false),
+      mHasEverBuiltInvisibleText(false),
+      mPendingInterruptFromTest(false),
+      mInterruptsEnabled(false),
+      mSendAfterPaintToContent(false),
+      mDrawImageBackground(true),  // always draw the background
+      mDrawColorBackground(true),
+      // mNeverAnimate is initialised below, in constructor body
+      mPaginated(aType != eContext_Galley),
+      mCanPaginatedScroll(false),
+      mDoScaledTwips(true),
+      mIsRootPaginatedDocument(false),
+      mPrefBidiDirection(false),
+      mPrefScrollbarSide(0),
+      mPendingThemeChanged(false),
+      mPendingThemeChangeKind(0),
+      mPendingUIResolutionChanged(false),
+      mPostedPrefChangedRunnable(false),
+      mIsGlyph(false),
+      mUsesExChUnits(false),
+      mCounterStylesDirty(true),
+      mFontFeatureValuesDirty(true),
+      mSuppressResizeReflow(false),
+      mIsVisual(false),
+      mPaintFlashing(false),
+      mPaintFlashingInitialized(false),
+      mHasWarnedAboutPositionedTableParts(false),
+      mHasWarnedAboutTooLargeDashedOrDottedRadius(false),
+      mQuirkSheetAdded(false),
+      mHadNonBlankPaint(false),
+      mHadContentfulPaint(false),
+      mHadContentfulPaintComposite(false)
+#ifdef DEBUG
+      ,
+      mInitialized(false)
+#endif
+{
+#ifdef DEBUG
+  PodZero(&mLayoutPhaseCount);
+#endif
+
+  if (!IsDynamic()) {
+    mImageAnimationMode = imgIContainer::kDontAnimMode;
+    mNeverAnimate = true;
+  } else {
+    mImageAnimationMode = imgIContainer::kNormalAnimMode;
+    mNeverAnimate = false;
+  }
+  NS_ASSERTION(mDocument, "Null document");
+
+  // if text perf logging enabled, init stats struct
+  if (MOZ_LOG_TEST(gfxPlatform::GetLog(eGfxLog_textperf), LogLevel::Warning)) {
+    mTextPerf = MakeUnique<gfxTextPerfMetrics>();
+  }
+
+  if (Preferences::GetBool(GFX_MISSING_FONTS_NOTIFY_PREF)) {
+    mMissingFonts = MakeUnique<gfxMissingFontRecorder>();
+  }
+
+  // TODO: check whether this is too expensive to do for all pages;
+  // maybe we could throttle and only collect stats on 1% of page-loads,
+  // or something like that.
+  mFontStats = MakeUnique<FontMatchingStats>();
+
+  if (StaticPrefs::layout_dynamic_toolbar_max_height() > 0) {
+    // The pref for dynamic toolbar max height is only used in reftests so it's
+    // fine to set here.
+    mDynamicToolbarMaxHeight = StaticPrefs::layout_dynamic_toolbar_max_height();
+  }
+}
+
+static const char* gExactCallbackPrefs[] = {
+    "browser.underline_anchors",
+    "browser.anchor_color",
+    "browser.active_color",
+    "browser.visited_color",
+    "image.animation_mode",
+    "dom.send_after_paint_to_content",
+    "layout.css.dpi",
+    "layout.css.devPixelsPerPx",
+    "nglayout.debug.paint_flashing",
+    "nglayout.debug.paint_flashing_chrome",
+    "intl.accept_languages",
+    "dom.meta-viewport.enabled",
+    nullptr,
+};
+
+static const char* gPrefixCallbackPrefs[] = {
+    "font.", "browser.display.",    "browser.viewport.",
+    "bidi.", "gfx.font_rendering.", nullptr,
+};
+
+void nsPresContext::Destroy() {
+  if (mEventManager) {
+    // unclear if these are needed, but can't hurt
+    mEventManager->NotifyDestroyPresContext(this);
+    mEventManager->SetPresContext(nullptr);
+    mEventManager = nullptr;
+  }
+
+  // Unregister preference callbacks
+  Preferences::UnregisterPrefixCallbacks(nsPresContext::PreferenceChanged,
+                                         gPrefixCallbackPrefs, this);
+  Preferences::UnregisterCallbacks(nsPresContext::PreferenceChanged,
+                                   gExactCallbackPrefs, this);
+
+  mRefreshDriver = nullptr;
+  MOZ_ASSERT(mOneShotPostRefreshObservers.IsEmpty());
+}
+
+nsPresContext::~nsPresContext() {
+  MOZ_ASSERT(!mPresShell, "Presshell forgot to clear our mPresShell pointer");
+  DetachPresShell();
+
+  Destroy();
+}
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsPresContext)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(nsPresContext)
+NS_IMPL_CYCLE_COLLECTING_RELEASE_WITH_LAST_RELEASE(nsPresContext, LastRelease())
+
+void nsPresContext::LastRelease() {
+  if (mMissingFonts) {
+    mMissingFonts->Clear();
+  }
+}
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(nsPresContext)
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsPresContext)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mAnimationEventDispatcher);
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocument);
+  // NS_IMPL_CYCLE_COLLECTION_TRAVERSE_RAWPTR(mDeviceContext); // not xpcom
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEffectCompositor);
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEventManager);
+  // NS_IMPL_CYCLE_COLLECTION_TRAVERSE_RAWPTR(mLanguage); // an atom
+
+  // NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mTheme); // a service
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPrintSettings);
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsPresContext)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mAnimationEventDispatcher);
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocument);
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDeviceContext);  // worth bothering?
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mEffectCompositor);
+  // NS_RELEASE(tmp->mLanguage); // an atom
+  // NS_IMPL_CYCLE_COLLECTION_UNLINK(mTheme); // a service
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mPrintSettings);
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_WEAK_PTR
+
+  tmp->Destroy();
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+// Set to true when LookAndFeelChanged needs to be called.  This is used
+// because the look and feel is a service, so there's no need to notify it from
+// more than one prescontext.
+static bool sLookAndFeelChanged;
+
+// Set to true when ThemeChanged needs to be called on mTheme.  This is used
+// because mTheme is a service, so there's no need to notify it from more than
+// one prescontext.
+static bool sThemeChanged;
+
+bool nsPresContext::IsChrome() const {
+  return Document()->IsInChromeDocShell();
+}
+
+void nsPresContext::GetUserPreferences() {
+  if (!GetPresShell()) {
+    // No presshell means nothing to do here.  We'll do this when we
+    // get a presshell.
+    return;
+  }
+
+  mAutoQualityMinFontSizePixelsPref =
+      Preferences::GetInt("browser.display.auto_quality_min_font_size");
+
+  PreferenceSheet::EnsureInitialized();
+
+  mSendAfterPaintToContent = Preferences::GetBool(
+      "dom.send_after_paint_to_content", mSendAfterPaintToContent);
+
+  mPrefScrollbarSide = Preferences::GetInt("layout.scrollbar.side");
+
+  Document()->SetMayNeedFontPrefsUpdate();
+
+  // * image animation
+  nsAutoCString animatePref;
+  Preferences::GetCString("image.animation_mode", animatePref);
+  if (animatePref.EqualsLiteral("normal"))
+    mImageAnimationModePref = imgIContainer::kNormalAnimMode;
+  else if (animatePref.EqualsLiteral("none"))
+    mImageAnimationModePref = imgIContainer::kDontAnimMode;
+  else if (animatePref.EqualsLiteral("once"))
+    mImageAnimationModePref = imgIContainer::kLoopOnceAnimMode;
+  else  // dynamic change to invalid value should act like it does initially
+    mImageAnimationModePref = imgIContainer::kNormalAnimMode;
+
+  uint32_t bidiOptions = GetBidi();
+
+  int32_t prefInt = Preferences::GetInt(IBMBIDI_TEXTDIRECTION_STR,
+                                        GET_BIDI_OPTION_DIRECTION(bidiOptions));
+  SET_BIDI_OPTION_DIRECTION(bidiOptions, prefInt);
+  mPrefBidiDirection = prefInt;
+
+  prefInt = Preferences::GetInt(IBMBIDI_TEXTTYPE_STR,
+                                GET_BIDI_OPTION_TEXTTYPE(bidiOptions));
+  SET_BIDI_OPTION_TEXTTYPE(bidiOptions, prefInt);
+
+  prefInt = Preferences::GetInt(IBMBIDI_NUMERAL_STR,
+                                GET_BIDI_OPTION_NUMERAL(bidiOptions));
+  SET_BIDI_OPTION_NUMERAL(bidiOptions, prefInt);
+
+  // We don't need to force reflow: either we are initializing a new
+  // prescontext or we are being called from UpdateAfterPreferencesChanged()
+  // which triggers a reflow anyway.
+  SetBidi(bidiOptions);
+}
+
+void nsPresContext::InvalidatePaintedLayers() {
+  if (!mPresShell) {
+    return;
+  }
+  if (nsIFrame* rootFrame = mPresShell->GetRootFrame()) {
+    // FrameLayerBuilder caches invalidation-related values that depend on the
+    // appunits-per-dev-pixel ratio, so ensure that all PaintedLayer drawing
+    // is completely flushed.
+    rootFrame->InvalidateFrameSubtree();
+  }
+}
+
+void nsPresContext::AppUnitsPerDevPixelChanged() {
+  int32_t oldAppUnitsPerDevPixel = mCurAppUnitsPerDevPixel;
+
+  InvalidatePaintedLayers();
+
+  if (mDeviceContext) {
+    mDeviceContext->FlushFontCache();
+  }
+
+  MediaFeatureValuesChanged(
+      {RestyleHint::RecascadeSubtree(), NS_STYLE_HINT_REFLOW,
+       MediaFeatureChangeReason::ResolutionChange},
+      MediaFeatureChangePropagation::JustThisDocument);
+
+  mCurAppUnitsPerDevPixel = mDeviceContext->AppUnitsPerDevPixel();
+
+  // Recompute the size for vh units since it's changed by the dynamic toolbar
+  // max height which is stored in screen coord.
+  if (IsRootContentDocumentCrossProcess()) {
+    AdjustSizeForViewportUnits();
+  }
+
+  // nsSubDocumentFrame uses a AppUnitsPerDevPixel difference between parent and
+  // child document to determine if it needs to build a nsDisplayZoom item. So
+  // if we that changes then we need to invalidate the subdoc frame so that
+  // item gets created/removed.
+  if (mPresShell) {
+    if (nsIFrame* frame = mPresShell->GetRootFrame()) {
+      frame = nsLayoutUtils::GetCrossDocParentFrame(frame);
+      if (frame) {
+        int32_t parentAPD = frame->PresContext()->AppUnitsPerDevPixel();
+        if ((parentAPD == oldAppUnitsPerDevPixel) !=
+            (parentAPD == mCurAppUnitsPerDevPixel)) {
+          frame->InvalidateFrame();
+        }
+      }
+    }
+  }
+
+  // We would also have to look at all of our child subdocuments but the
+  // InvalidatePaintedLayers call above calls InvalidateFrameSubtree which
+  // would invalidate all subdocument frames already.
+}
+
+// static
+void nsPresContext::PreferenceChanged(const char* aPrefName, void* aSelf) {
+  static_cast<nsPresContext*>(aSelf)->PreferenceChanged(aPrefName);
+}
+
+void nsPresContext::PreferenceChanged(const char* aPrefName) {
+  nsDependentCString prefName(aPrefName);
+  if (prefName.EqualsLiteral("layout.css.dpi") ||
+      prefName.EqualsLiteral("layout.css.devPixelsPerPx")) {
+    int32_t oldAppUnitsPerDevPixel = mDeviceContext->AppUnitsPerDevPixel();
+    // We need to assume the DPI changes, since `mDeviceContext` is shared with
+    // other documents, and we'd need to save the return value of the first call
+    // for all of them.
+    Unused << mDeviceContext->CheckDPIChange();
+    if (mPresShell) {
+      OwningNonNull<mozilla::PresShell> presShell(*mPresShell);
+      // Re-fetch the view manager's window dimensions in case there's a
+      // deferred resize which hasn't affected our mVisibleArea yet
+      nscoord oldWidthAppUnits, oldHeightAppUnits;
+      RefPtr<nsViewManager> vm = presShell->GetViewManager();
+      if (!vm) {
+        return;
+      }
+      vm->GetWindowDimensions(&oldWidthAppUnits, &oldHeightAppUnits);
+      float oldWidthDevPixels = oldWidthAppUnits / oldAppUnitsPerDevPixel;
+      float oldHeightDevPixels = oldHeightAppUnits / oldAppUnitsPerDevPixel;
+
+      AppUnitsPerDevPixelChanged();
+
+      nscoord width = NSToCoordRound(oldWidthDevPixels * AppUnitsPerDevPixel());
+      nscoord height =
+          NSToCoordRound(oldHeightDevPixels * AppUnitsPerDevPixel());
+      vm->SetWindowDimensions(width, height);
+    }
+    return;
+  }
+
+  if (StringBeginsWith(prefName, "browser.viewport."_ns) ||
+      StringBeginsWith(prefName, "font.size.inflation."_ns) ||
+      prefName.EqualsLiteral("dom.meta-viewport.enabled")) {
+    if (mPresShell) {
+      mPresShell->MaybeReflowForInflationScreenSizeChange();
+    }
+  }
+
+  // Changing any of these potentially changes the value of @media
+  // (prefers-contrast).
+  if (prefName.EqualsLiteral("layout.css.prefers-contrast.enabled") ||
+      prefName.EqualsLiteral("browser.display.document_color_use") ||
+      prefName.EqualsLiteral("privacy.resistFingerprinting") ||
+      prefName.EqualsLiteral("browser.display.foreground_color") ||
+      prefName.EqualsLiteral("browser.display.background_color")) {
+    MediaFeatureValuesChanged({MediaFeatureChangeReason::PreferenceChange},
+                              MediaFeatureChangePropagation::JustThisDocument);
+  }
+  if (prefName.EqualsLiteral(GFX_MISSING_FONTS_NOTIFY_PREF)) {
+    if (Preferences::GetBool(GFX_MISSING_FONTS_NOTIFY_PREF)) {
+      if (!mMissingFonts) {
+        mMissingFonts = MakeUnique<gfxMissingFontRecorder>();
+        // trigger reflow to detect missing fonts on the current page
+        mChangeHintForPrefChange |= NS_STYLE_HINT_REFLOW;
+      }
+    } else {
+      if (mMissingFonts) {
+        mMissingFonts->Clear();
+      }
+      mMissingFonts = nullptr;
+    }
+  }
+  if (prefName.EqualsLiteral("font.internaluseonly.changed") &&
+      !IsPrintingOrPrintPreview()) {
+    // If there's a change to the font list, we generally need to reconstruct
+    // frames, as the existing frames may be referring to fonts that are no
+    // longer available. But in the case of a static-clone document used for
+    // printing or print-preview, this is undesirable because the nsPrintJob
+    // is holding weak refs to frames that will get blown away unexpectedly by
+    // this reconstruction. So the prescontext for a print/preview doc ignores
+    // the font-list update.
+    //
+    // This means the print document may still be using cached fonts that are
+    // no longer present in the font list, but that should be safe given that
+    // all the required font instances have already been created, so it won't
+    // be depending on access to the font-list entries.
+    //
+    // XXX Actually, I think it's probably a bad idea to do *any* restyling of
+    // print documents in response to pref changes. We could be in the middle
+    // of printing the document, and reflowing all the frames might cause some
+    // kind of unwanted mid-document discontinuity.
+    mChangeHintForPrefChange |= nsChangeHint_ReconstructFrame;
+  } else if (StringBeginsWith(prefName, "font."_ns) ||
+             // Changes to font family preferences don't change anything in the
+             // computed style data, so the style system won't generate a reflow
+             // hint for us.  We need to do that manually.
+             prefName.EqualsLiteral("intl.accept_languages") ||
+             // Changes to bidi prefs need to trigger a reflow (see bug 443629)
+             StringBeginsWith(prefName, "bidi."_ns) ||
+             // Changes to font_rendering prefs need to trigger a reflow
+             StringBeginsWith(prefName, "gfx.font_rendering."_ns)) {
+    mChangeHintForPrefChange |= NS_STYLE_HINT_REFLOW;
+  }
+
+  // We will end up calling InvalidatePreferenceSheets one from each pres
+  // context, but all it's doing is clearing its cached sheet pointers, so it
+  // won't be wastefully recreating the sheet multiple times.
+  //
+  // The first pres context that has its pref changed runnable called will
+  // be the one to cause the reconstruction of the pref style sheet.
+  GlobalStyleSheetCache::InvalidatePreferenceSheets();
+  PreferenceSheet::Refresh();
+  DispatchPrefChangedRunnableIfNeeded();
+
+  if (prefName.EqualsLiteral("nglayout.debug.paint_flashing") ||
+      prefName.EqualsLiteral("nglayout.debug.paint_flashing_chrome")) {
+    mPaintFlashingInitialized = false;
+    return;
+  }
+}
+
+void nsPresContext::DispatchPrefChangedRunnableIfNeeded() {
+  if (mPostedPrefChangedRunnable) {
+    return;
+  }
+
+  nsCOMPtr<nsIRunnable> runnable =
+      NewRunnableMethod("nsPresContext::UpdateAfterPreferencesChanged", this,
+                        &nsPresContext::UpdateAfterPreferencesChanged);
+  nsresult rv = Document()->Dispatch(TaskCategory::Other, runnable.forget());
+  if (NS_SUCCEEDED(rv)) {
+    mPostedPrefChangedRunnable = true;
+  }
+}
+
+void nsPresContext::UpdateAfterPreferencesChanged() {
+  mPostedPrefChangedRunnable = false;
+  if (!mPresShell) {
+    return;
+  }
+
+  if (mDocument->IsInChromeDocShell()) {
+    // FIXME(emilio): Do really all these prefs not affect chrome docs? I
+    // suspect we should move this check somewhere else.
+    return;
+  }
+
+  StaticPresData::Get()->InvalidateFontPrefs();
+
+  // Initialize our state from the user preferences
+  GetUserPreferences();
+
+  // update the presShell: tell it to set the preference style rules up
+  mPresShell->UpdatePreferenceStyles();
+
+  InvalidatePaintedLayers();
+  mDeviceContext->FlushFontCache();
+
+  // Preferences require rerunning selector matching because we rebuild
+  // the pref style sheet for some preference changes.
+  RebuildAllStyleData(mChangeHintForPrefChange, RestyleHint::RestyleSubtree());
+  mChangeHintForPrefChange = nsChangeHint(0);
+}
+
+nsresult nsPresContext::Init(nsDeviceContext* aDeviceContext) {
+  NS_ASSERTION(!mInitialized, "attempt to reinit pres context");
+  NS_ENSURE_ARG(aDeviceContext);
+
+  mDeviceContext = aDeviceContext;
+
+  // In certain rare cases (such as changing page mode), we tear down layout
+  // state and re-initialize a new prescontext for a document. Given that we
+  // hang style state off the DOM, we detect that re-initialization case and
+  // lazily drop the servo data. We don't do this eagerly during layout teardown
+  // because that would incur an extra whole-tree traversal that's unnecessary
+  // most of the time.
+  //
+  // FIXME(emilio): I'm pretty sure this doesn't happen after bug 1414999.
+  Element* root = mDocument->GetRootElement();
+  if (root && root->HasServoData()) {
+    RestyleManager::ClearServoDataFromSubtree(root);
+  }
+
+  if (mDeviceContext->SetFullZoom(mFullZoom)) {
+    mDeviceContext->FlushFontCache();
+  }
+  mCurAppUnitsPerDevPixel = mDeviceContext->AppUnitsPerDevPixel();
+
+  mEventManager = new mozilla::EventStateManager();
+
+  mAnimationEventDispatcher = new mozilla::AnimationEventDispatcher(this);
+  mEffectCompositor = new mozilla::EffectCompositor(this);
+  mTransitionManager = MakeUnique<nsTransitionManager>(this);
+  mAnimationManager = MakeUnique<nsAnimationManager>(this);
+
+  if (mDocument->GetDisplayDocument()) {
+    NS_ASSERTION(mDocument->GetDisplayDocument()->GetPresContext(),
+                 "Why are we being initialized?");
+    mRefreshDriver =
+        mDocument->GetDisplayDocument()->GetPresContext()->RefreshDriver();
+  } else {
+    dom::Document* parent = mDocument->GetInProcessParentDocument();
+    // Unfortunately, sometimes |parent| here has no presshell because
+    // printing screws up things.  Assert that in other cases it does,
+    // but whenever the shell is null just fall back on using our own
+    // refresh driver.
+    NS_ASSERTION(
+        !parent || mDocument->IsStaticDocument() || parent->GetPresShell(),
+        "How did we end up with a presshell if our parent doesn't "
+        "have one?");
+    if (parent && parent->GetPresContext()) {
+      // XXX the document can change in AttachPresShell, does this work?
+      dom::BrowsingContext* browsingContext = mDocument->GetBrowsingContext();
+      if (browsingContext && !browsingContext->IsTop()) {
+        Element* containingElement =
+            parent->FindContentForSubDocument(mDocument);
+        if (!containingElement->IsXULElement() ||
+            !containingElement->HasAttr(kNameSpaceID_None,
+                                        nsGkAtoms::forceOwnRefreshDriver)) {
+          mRefreshDriver = parent->GetPresContext()->RefreshDriver();
+        }
+      }
+    }
+
+    if (!mRefreshDriver) {
+      mRefreshDriver = new nsRefreshDriver(this);
+    }
+  }
+
+  // Register callbacks so we're notified when the preferences change
+  Preferences::RegisterPrefixCallbacks(nsPresContext::PreferenceChanged,
+                                       gPrefixCallbackPrefs, this);
+  Preferences::RegisterCallbacks(nsPresContext::PreferenceChanged,
+                                 gExactCallbackPrefs, this);
+
+  nsresult rv = mEventManager->Init();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mEventManager->SetPresContext(this);
+
+#if defined(MOZ_WIDGET_ANDROID)
+  if (IsRootContentDocumentCrossProcess() &&
+      MOZ_LIKELY(
+          !Preferences::HasUserValue("layout.dynamic-toolbar-max-height"))) {
+    if (BrowserChild* browserChild =
+            BrowserChild::GetFrom(mDocument->GetDocShell())) {
+      mDynamicToolbarMaxHeight = browserChild->GetDynamicToolbarMaxHeight();
+      mDynamicToolbarHeight = mDynamicToolbarMaxHeight;
+    }
+  }
+#endif
+
+#ifdef DEBUG
+  mInitialized = true;
+#endif
+
+  return NS_OK;
+}
+
+// Note: We don't hold a reference on the shell; it has a reference to
+// us
+void nsPresContext::AttachPresShell(mozilla::PresShell* aPresShell) {
+  MOZ_ASSERT(!mPresShell);
+  mPresShell = aPresShell;
+
+  mRestyleManager = MakeUnique<mozilla::RestyleManager>(this);
+
+  // Since CounterStyleManager is also the name of a method of
+  // nsPresContext, it is necessary to prefix the class with the mozilla
+  // namespace here.
+  mCounterStyleManager = new mozilla::CounterStyleManager(this);
+
+  dom::Document* doc = mPresShell->GetDocument();
+  MOZ_ASSERT(doc);
+  // Have to update PresContext's mDocument before calling any other methods.
+  mDocument = doc;
+  // Initialize our state from the user preferences, now that we
+  // have a presshell, and hence a document.
+  GetUserPreferences();
+
+  nsIURI* docURI = doc->GetDocumentURI();
+
+  if (IsDynamic() && docURI) {
+    if (!docURI->SchemeIs("chrome") && !docURI->SchemeIs("resource"))
+      mImageAnimationMode = mImageAnimationModePref;
+    else
+      mImageAnimationMode = imgIContainer::kNormalAnimMode;
+  }
+
+  UpdateCharSet(doc->GetDocumentCharacterSet());
+}
+
+void nsPresContext::RecomputeBrowsingContextDependentData() {
+  MOZ_ASSERT(mDocument);
+  dom::Document* doc = mDocument;
+  // Resource documents inherit all this state from their display document.
+  while (dom::Document* outer = doc->GetDisplayDocument()) {
+    doc = outer;
+  }
+  auto* browsingContext = doc->GetBrowsingContext();
+  if (!browsingContext) {
+    // This can legitimately happen for e.g. SVG images. Those just get scaled
+    // as a result of the zoom on the embedder document so it doesn't really
+    // matter...
+    return;
+  }
+  SetFullZoom(browsingContext->FullZoom());
+  SetTextZoom(browsingContext->TextZoom());
+  mDocument->EnumerateExternalResources([](dom::Document& aSubResource) {
+    if (nsPresContext* subResourcePc = aSubResource.GetPresContext()) {
+      subResourcePc->RecomputeBrowsingContextDependentData();
+    }
+    return CallState::Continue;
+  });
+}
+
+void nsPresContext::DetachPresShell() {
+  // The counter style manager's destructor needs to deallocate with the
+  // presshell arena. Disconnect it before nulling out the shell.
+  //
+  // XXXbholley: Given recent refactorings, it probably makes more sense to
+  // just null our mPresShell at the bottom of this function. I'm leaving it
+  // this way to preserve the old ordering, but I doubt anything would break.
+  if (mCounterStyleManager) {
+    mCounterStyleManager->Disconnect();
+    mCounterStyleManager = nullptr;
+  }
+
+  mPresShell = nullptr;
+
+  if (mAnimationEventDispatcher) {
+    mAnimationEventDispatcher->Disconnect();
+    mAnimationEventDispatcher = nullptr;
+  }
+  if (mEffectCompositor) {
+    mEffectCompositor->Disconnect();
+    mEffectCompositor = nullptr;
+  }
+  if (mTransitionManager) {
+    mTransitionManager->Disconnect();
+    mTransitionManager = nullptr;
+  }
+  if (mAnimationManager) {
+    mAnimationManager->Disconnect();
+    mAnimationManager = nullptr;
+  }
+  if (mRestyleManager) {
+    mRestyleManager->Disconnect();
+    mRestyleManager = nullptr;
+  }
+  if (mRefreshDriver && mRefreshDriver->GetPresContext() == this) {
+    mRefreshDriver->Disconnect();
+    // Can't null out the refresh driver here.
+  }
+
+  if (IsRoot()) {
+    nsRootPresContext* thisRoot = static_cast<nsRootPresContext*>(this);
+
+    // Have to cancel our plugin geometry timer, because the
+    // callback for that depends on a non-null presshell.
+    thisRoot->CancelApplyPluginGeometryTimer();
+  }
+}
+
+void nsPresContext::DocumentCharSetChanged(NotNull<const Encoding*> aCharSet) {
+  UpdateCharSet(aCharSet);
+  mDeviceContext->FlushFontCache();
+
+  // If a document contains one or more <script> elements, frame construction
+  // might happen earlier than the UpdateCharSet(), so we need to restyle
+  // descendants to make their style data up-to-date.
+  //
+  // FIXME(emilio): Revisit whether this is true after bug 1438911.
+  RebuildAllStyleData(NS_STYLE_HINT_REFLOW, RestyleHint::RecascadeSubtree());
+}
+
+void nsPresContext::UpdateCharSet(NotNull<const Encoding*> aCharSet) {
+  switch (GET_BIDI_OPTION_TEXTTYPE(GetBidi())) {
+    case IBMBIDI_TEXTTYPE_LOGICAL:
+      SetVisualMode(false);
+      break;
+
+    case IBMBIDI_TEXTTYPE_VISUAL:
+      SetVisualMode(true);
+      break;
+
+    case IBMBIDI_TEXTTYPE_CHARSET:
+    default:
+      SetVisualMode(IsVisualCharset(aCharSet));
+  }
+}
+
+nsPresContext* nsPresContext::GetParentPresContext() const {
+  mozilla::PresShell* presShell = GetPresShell();
+  if (presShell) {
+    nsViewManager* viewManager = presShell->GetViewManager();
+    if (viewManager) {
+      nsView* view = viewManager->GetRootView();
+      if (view) {
+        view = view->GetParent();  // anonymous inner view
+        if (view) {
+          view = view->GetParent();  // subdocumentframe's view
+          if (view) {
+            nsIFrame* f = view->GetFrame();
+            if (f) {
+              return f->PresContext();
+            }
+          }
+        }
+      }
+    }
+  }
+  return nullptr;
+}
+
+nsPresContext* nsPresContext::GetInProcessRootContentDocumentPresContext() {
+  if (IsChrome()) return nullptr;
+  nsPresContext* pc = this;
+  for (;;) {
+    nsPresContext* parent = pc->GetParentPresContext();
+    if (!parent || parent->IsChrome()) return pc;
+    pc = parent;
+  }
+}
+
+nsIWidget* nsPresContext::GetNearestWidget(nsPoint* aOffset) {
+  NS_ENSURE_TRUE(mPresShell, nullptr);
+  nsViewManager* vm = mPresShell->GetViewManager();
+  NS_ENSURE_TRUE(vm, nullptr);
+  nsView* rootView = vm->GetRootView();
+  NS_ENSURE_TRUE(rootView, nullptr);
+  return rootView->GetNearestWidget(aOffset);
+}
+
+nsIWidget* nsPresContext::GetRootWidget() const {
+  NS_ENSURE_TRUE(mPresShell, nullptr);
+  nsViewManager* vm = mPresShell->GetViewManager();
+  if (!vm) {
+    return nullptr;
+  }
+  nsCOMPtr<nsIWidget> widget;
+  vm->GetRootWidget(getter_AddRefs(widget));
+  return widget.get();
+}
+
+// We may want to replace this with something faster, maybe caching the root
+// prescontext
+nsRootPresContext* nsPresContext::GetRootPresContext() const {
+  nsPresContext* pc = const_cast<nsPresContext*>(this);
+  for (;;) {
+    nsPresContext* parent = pc->GetParentPresContext();
+    if (!parent) break;
+    pc = parent;
+  }
+  return pc->IsRoot() ? static_cast<nsRootPresContext*>(pc) : nullptr;
+}
+
+// Helper function for setting Anim Mode on image
+static void SetImgAnimModeOnImgReq(imgIRequest* aImgReq, uint16_t aMode) {
+  if (aImgReq) {
+    nsCOMPtr<imgIContainer> imgCon;
+    aImgReq->GetImage(getter_AddRefs(imgCon));
+    if (imgCon) {
+      imgCon->SetAnimationMode(aMode);
+    }
+  }
+}
+
+// IMPORTANT: Assumption is that all images for a Presentation
+// have the same Animation Mode (pavlov said this was OK)
+//
+// Walks content and set the animation mode
+// this is a way to turn on/off image animations
+void nsPresContext::SetImgAnimations(nsIContent* aParent, uint16_t aMode) {
+  nsCOMPtr<nsIImageLoadingContent> imgContent(do_QueryInterface(aParent));
+  if (imgContent) {
+    nsCOMPtr<imgIRequest> imgReq;
+    imgContent->GetRequest(nsIImageLoadingContent::CURRENT_REQUEST,
+                           getter_AddRefs(imgReq));
+    SetImgAnimModeOnImgReq(imgReq, aMode);
+  }
+
+  for (nsIContent* childContent = aParent->GetFirstChild(); childContent;
+       childContent = childContent->GetNextSibling()) {
+    SetImgAnimations(childContent, aMode);
+  }
+}
+
+void nsPresContext::SetSMILAnimations(dom::Document* aDoc, uint16_t aNewMode,
+                                      uint16_t aOldMode) {
+  if (aDoc->HasAnimationController()) {
+    SMILAnimationController* controller = aDoc->GetAnimationController();
+    switch (aNewMode) {
+      case imgIContainer::kNormalAnimMode:
+      case imgIContainer::kLoopOnceAnimMode:
+        if (aOldMode == imgIContainer::kDontAnimMode)
+          controller->Resume(SMILTimeContainer::PAUSE_USERPREF);
+        break;
+
+      case imgIContainer::kDontAnimMode:
+        if (aOldMode != imgIContainer::kDontAnimMode)
+          controller->Pause(SMILTimeContainer::PAUSE_USERPREF);
+        break;
+    }
+  }
+}
+
+void nsPresContext::SetImageAnimationMode(uint16_t aMode) {
+  NS_ASSERTION(aMode == imgIContainer::kNormalAnimMode ||
+                   aMode == imgIContainer::kDontAnimMode ||
+                   aMode == imgIContainer::kLoopOnceAnimMode,
+               "Wrong Animation Mode is being set!");
+
+  // Image animation mode cannot be changed when rendering to a printer.
+  if (!IsDynamic()) return;
+
+  // Now walk the content tree and set the animation mode
+  // on all the images.
+  if (mPresShell) {
+    dom::Document* doc = mPresShell->GetDocument();
+    if (doc) {
+      doc->StyleImageLoader()->SetAnimationMode(aMode);
+
+      Element* rootElement = doc->GetRootElement();
+      if (rootElement) {
+        SetImgAnimations(rootElement, aMode);
+      }
+      SetSMILAnimations(doc, aMode, mImageAnimationMode);
+    }
+  }
+
+  mImageAnimationMode = aMode;
+}
+
+void nsPresContext::UpdateEffectiveTextZoom() {
+  float newZoom = mSystemFontScale * mTextZoom;
+  float minZoom = StaticPrefs::zoom_minPercent() / 100.0f;
+  float maxZoom = StaticPrefs::zoom_maxPercent() / 100.0f;
+
+  if (newZoom < minZoom) {
+    newZoom = minZoom;
+  } else if (newZoom > maxZoom) {
+    newZoom = maxZoom;
+  }
+
+  mEffectiveTextZoom = newZoom;
+
+  // Media queries could have changed, since we changed the meaning
+  // of 'em' units in them.
+  MediaFeatureValuesChanged(
+      {RestyleHint::RecascadeSubtree(), NS_STYLE_HINT_REFLOW,
+       MediaFeatureChangeReason::ZoomChange},
+      MediaFeatureChangePropagation::JustThisDocument);
+}
+
+float nsPresContext::GetDeviceFullZoom() {
+  return mDeviceContext->GetFullZoom();
+}
+
+void nsPresContext::SetFullZoom(float aZoom) {
+  if (!mPresShell || mFullZoom == aZoom) {
+    return;
+  }
+
+  // Re-fetch the view manager's window dimensions in case there's a deferred
+  // resize which hasn't affected our mVisibleArea yet
+  nscoord oldWidthAppUnits, oldHeightAppUnits;
+  mPresShell->GetViewManager()->GetWindowDimensions(&oldWidthAppUnits,
+                                                    &oldHeightAppUnits);
+  float oldWidthDevPixels = oldWidthAppUnits / float(mCurAppUnitsPerDevPixel);
+  float oldHeightDevPixels = oldHeightAppUnits / float(mCurAppUnitsPerDevPixel);
+  mDeviceContext->SetFullZoom(aZoom);
+
+  NS_ASSERTION(!mSuppressResizeReflow,
+               "two zooms happening at the same time? Impossible!");
+
+  // We can't suppress the resize reflow if we support APZ zooming, as MVM
+  // relies on ResizeReflowIgnoreOverride() actually updating layout to update
+  // the viewport based on that.
+  RefPtr<MobileViewportManager> mvm = mPresShell->GetMobileViewportManager();
+  mSuppressResizeReflow = !mvm;
+
+  mFullZoom = aZoom;
+
+  AppUnitsPerDevPixelChanged();
+
+  mPresShell->GetViewManager()->SetWindowDimensions(
+      NSToCoordRound(oldWidthDevPixels * AppUnitsPerDevPixel()),
+      NSToCoordRound(oldHeightDevPixels * AppUnitsPerDevPixel()));
+
+  mSuppressResizeReflow = false;
+}
+
+void nsPresContext::SetOverrideDPPX(float aDPPX) {
+  // SetOverrideDPPX is called during navigations, including history
+  // traversals.  In that case, it's typically called with our current value,
+  // and we don't need to actually do anything.
+  if (aDPPX == GetOverrideDPPX()) {
+    return;
+  }
+
+  mMediaEmulationData.mDPPX = aDPPX;
+  MediaFeatureValuesChanged({MediaFeatureChangeReason::ResolutionChange},
+                            MediaFeatureChangePropagation::JustThisDocument);
+}
+
+void nsPresContext::SetOverridePrefersColorScheme(
+    const Maybe<StylePrefersColorScheme>& aOverride) {
+  if (GetOverridePrefersColorScheme() == aOverride) {
+    return;
+  }
+  mMediaEmulationData.mPrefersColorScheme = aOverride;
+  // This is a bit of a lie, but it's the code-path that gets taken for regular
+  // system metrics changes via ThemeChanged().
+  MediaFeatureValuesChanged({MediaFeatureChangeReason::SystemMetricsChange},
+                            MediaFeatureChangePropagation::JustThisDocument);
+}
+
+gfxSize nsPresContext::ScreenSizeInchesForFontInflation(bool* aChanged) {
+  if (aChanged) {
+    *aChanged = false;
+  }
+
+  nsDeviceContext* dx = DeviceContext();
+  nsRect clientRect;
+  dx->GetClientRect(clientRect);  // FIXME: GetClientRect looks expensive
+  float unitsPerInch = dx->AppUnitsPerPhysicalInch();
+  gfxSize deviceSizeInches(float(clientRect.width) / unitsPerInch,
+                           float(clientRect.height) / unitsPerInch);
+
+  if (mLastFontInflationScreenSize == gfxSize(-1.0, -1.0)) {
+    mLastFontInflationScreenSize = deviceSizeInches;
+  }
+
+  if (deviceSizeInches != mLastFontInflationScreenSize && aChanged) {
+    *aChanged = true;
+    mLastFontInflationScreenSize = deviceSizeInches;
+  }
+
+  return deviceSizeInches;
+}
+
+static bool CheckOverflow(const ComputedStyle* aComputedStyle,
+                          ScrollStyles* aStyles) {
+  // If they're not styled yet, we'll get around to it when constructing frames
+  // for the element.
+  if (!aComputedStyle) {
+    return false;
+  }
+  const nsStyleDisplay* display = aComputedStyle->StyleDisplay();
+
+  // If they will generate no box, just don't.
+  if (display->mDisplay == StyleDisplay::None ||
+      display->mDisplay == StyleDisplay::Contents) {
+    return false;
+  }
+
+  // NOTE(emilio): This check needs to match the one in
+  // Document::IsPotentiallyScrollable.
+  if (display->OverflowIsVisibleInBothAxis()) {
+    return false;
+  }
+
+  *aStyles =
+      ScrollStyles(*display, ScrollStyles::MapOverflowToValidScrollStyle);
+  return true;
+}
+
+// https://drafts.csswg.org/css-overflow/#overflow-propagation
+//
+// NOTE(emilio): We may need to use out-of-date styles for this, since this is
+// called from nsCSSFrameConstructor::ContentRemoved. We could refactor this a
+// bit to avoid doing that, and also fix correctness issues (we don't invalidate
+// properly when we insert a body element and there is a previous one, for
+// example).
+static Element* GetPropagatedScrollStylesForViewport(
+    nsPresContext* aPresContext, ScrollStyles* aStyles) {
+  Document* document = aPresContext->Document();
+  Element* docElement = document->GetRootElement();
+  // docElement might be null if we're doing this after removing it.
+  if (!docElement) {
+    return nullptr;
+  }
+
+  // Check the style on the document root element
+  const auto* rootStyle = Servo_Element_GetMaybeOutOfDateStyle(docElement);
+  if (CheckOverflow(rootStyle, aStyles)) {
+    // tell caller we stole the overflow style from the root element
+    return docElement;
+  }
+
+  // Don't look in the BODY for non-HTML documents or HTML documents
+  // with non-HTML roots.
+  // XXX this should be earlier; we shouldn't even look at the document root
+  // for non-HTML documents. Fix this once we support explicit CSS styling
+  // of the viewport
+  if (!document->IsHTMLOrXHTML() || !docElement->IsHTMLElement()) {
+    return nullptr;
+  }
+
+  Element* bodyElement = document->AsHTMLDocument()->GetBodyElement();
+  if (!bodyElement) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(bodyElement->IsHTMLElement(nsGkAtoms::body),
+             "GetBodyElement returned something bogus");
+
+  const auto* bodyStyle = Servo_Element_GetMaybeOutOfDateStyle(bodyElement);
+  if (CheckOverflow(bodyStyle, aStyles)) {
+    // tell caller we stole the overflow style from the body element
+    return bodyElement;
+  }
+
+  return nullptr;
+}
+
+Element* nsPresContext::UpdateViewportScrollStylesOverride() {
+  // Start off with our default styles, and then update them as needed.
+  mViewportScrollStyles =
+      ScrollStyles(StyleOverflow::Auto, StyleOverflow::Auto);
+  mViewportScrollOverrideElement = nullptr;
+  // Don't propagate the scrollbar state in printing or print preview.
+  if (!IsPaginated()) {
+    mViewportScrollOverrideElement =
+        GetPropagatedScrollStylesForViewport(this, &mViewportScrollStyles);
+  }
+
+  dom::Document* document = Document();
+  if (Element* fullscreenElement = document->GetFullscreenElement()) {
+    // If the document is in fullscreen, but the fullscreen element is
+    // not the root element, we should explicitly suppress the scrollbar
+    // here. Note that, we still need to return the original element
+    // the styles are from, so that the state of those elements is not
+    // affected across fullscreen change.
+    if (fullscreenElement != document->GetRootElement() &&
+        fullscreenElement != mViewportScrollOverrideElement) {
+      mViewportScrollStyles =
+          ScrollStyles(StyleOverflow::Hidden, StyleOverflow::Hidden);
+    }
+  }
+  return mViewportScrollOverrideElement;
+}
+
+bool nsPresContext::ElementWouldPropagateScrollStyles(const Element& aElement) {
+  if (aElement.GetParent() && !aElement.IsHTMLElement(nsGkAtoms::body)) {
+    // We certainly won't be propagating from this element.
+    return false;
+  }
+
+  // Go ahead and just call GetPropagatedScrollStylesForViewport, but update
+  // a dummy ScrollStyles we don't care about.  It'll do a bit of extra work,
+  // but saves us having to have more complicated code or more code duplication;
+  // in practice we will make this call quite rarely, because we checked for all
+  // the common cases above.
+  ScrollStyles dummy(StyleOverflow::Auto, StyleOverflow::Auto);
+  return GetPropagatedScrollStylesForViewport(this, &dummy) == &aElement;
+}
+
+nsISupports* nsPresContext::GetContainerWeak() const {
+  return mDocument->GetDocShell();
+}
+
+nsDocShell* nsPresContext::GetDocShell() const {
+  return nsDocShell::Cast(mDocument->GetDocShell());
+}
+
+bool nsPresContext::BidiEnabled() const { return Document()->GetBidiEnabled(); }
+
+void nsPresContext::SetBidiEnabled() const { Document()->SetBidiEnabled(); }
+
+void nsPresContext::SetBidi(uint32_t aSource) {
+  // Don't do all this stuff unless the options have changed.
+  if (aSource == GetBidi()) {
+    return;
+  }
+
+  Document()->SetBidiOptions(aSource);
+  if (IBMBIDI_TEXTDIRECTION_RTL == GET_BIDI_OPTION_DIRECTION(aSource) ||
+      IBMBIDI_NUMERAL_HINDI == GET_BIDI_OPTION_NUMERAL(aSource)) {
+    SetBidiEnabled();
+  }
+  if (IBMBIDI_TEXTTYPE_VISUAL == GET_BIDI_OPTION_TEXTTYPE(aSource)) {
+    SetVisualMode(true);
+  } else if (IBMBIDI_TEXTTYPE_LOGICAL == GET_BIDI_OPTION_TEXTTYPE(aSource)) {
+    SetVisualMode(false);
+  } else {
+    SetVisualMode(IsVisualCharset(Document()->GetDocumentCharacterSet()));
+  }
+}
+
+uint32_t nsPresContext::GetBidi() const { return Document()->GetBidiOptions(); }
+
+void nsPresContext::RecordInteractionTime(InteractionType aType,
+                                          const TimeStamp& aTimeStamp) {
+  if (!mInteractionTimeEnabled || aTimeStamp.IsNull()) {
+    return;
+  }
+
+  // Array of references to the member variable of each time stamp
+  // for the different interaction types, keyed by InteractionType.
+  TimeStamp nsPresContext::*interactionTimes[] = {
+      &nsPresContext::mFirstClickTime, &nsPresContext::mFirstKeyTime,
+      &nsPresContext::mFirstMouseMoveTime, &nsPresContext::mFirstScrollTime};
+
+  // Array of histogram IDs for the different interaction types,
+  // keyed by InteractionType.
+  Telemetry::HistogramID histogramIds[] = {
+      Telemetry::TIME_TO_FIRST_CLICK_MS, Telemetry::TIME_TO_FIRST_KEY_INPUT_MS,
+      Telemetry::TIME_TO_FIRST_MOUSE_MOVE_MS,
+      Telemetry::TIME_TO_FIRST_SCROLL_MS};
+
+  TimeStamp& interactionTime =
+      this->*(interactionTimes[static_cast<uint32_t>(aType)]);
+  if (!interactionTime.IsNull()) {
+    // We have already recorded an interaction time.
+    return;
+  }
+
+  // Record the interaction time if it occurs after the first paint
+  // of the top level content document.
+  nsPresContext* inProcessRootPresContext =
+      GetInProcessRootContentDocumentPresContext();
+
+  if (!inProcessRootPresContext ||
+      !inProcessRootPresContext->IsRootContentDocumentCrossProcess()) {
+    // There is no top content pres context, or we are in a cross process
+    // document so we don't care about the interaction time. Record a value
+    // anyways to avoid trying to find the top content pres context in future
+    // interactions.
+    interactionTime = TimeStamp::Now();
+    return;
+  }
+
+  if (inProcessRootPresContext->mFirstNonBlankPaintTime.IsNull() ||
+      inProcessRootPresContext->mFirstNonBlankPaintTime > aTimeStamp) {
+    // Top content pres context has not had a non-blank paint yet
+    // or the event timestamp is before the first non-blank paint,
+    // so don't record interaction time.
+    return;
+  }
+
+  // Check if we are recording the first of any of the interaction types.
+  bool isFirstInteraction = true;
+  for (TimeStamp nsPresContext::*memberPtr : interactionTimes) {
+    TimeStamp& timeStamp = this->*(memberPtr);
+    if (!timeStamp.IsNull()) {
+      isFirstInteraction = false;
+      break;
+    }
+  }
+
+  interactionTime = TimeStamp::Now();
+  // Only the top level content pres context reports first interaction
+  // time to telemetry (if it hasn't already done so).
+  if (this == inProcessRootPresContext) {
+    if (Telemetry::CanRecordExtended()) {
+      double millis =
+          (interactionTime - mFirstNonBlankPaintTime).ToMilliseconds();
+      Telemetry::Accumulate(histogramIds[static_cast<uint32_t>(aType)], millis);
+
+      if (isFirstInteraction) {
+        Telemetry::Accumulate(Telemetry::TIME_TO_FIRST_INTERACTION_MS, millis);
+
+        if (Document()->ShouldIncludeInTelemetry(
+                /* aAllowExtensionURIs = */ false)) {
+          if (auto* wgc = Document()->GetWindowGlobalChild()) {
+            Unused << wgc->SendSubmitTimeToFirstInteractionPreloadTelemetry(
+                millis);
+          }
+        }
+      }
+    }
+  } else {
+    inProcessRootPresContext->RecordInteractionTime(aType, aTimeStamp);
+  }
+}
+
+nsITheme* nsPresContext::EnsureTheme() {
+  MOZ_ASSERT(!mTheme);
+  if (Document()->ShouldAvoidNativeTheme()) {
+    mTheme = do_GetBasicNativeThemeDoNotUseDirectly();
+  } else {
+    mTheme = do_GetNativeThemeDoNotUseDirectly();
+  }
+  MOZ_RELEASE_ASSERT(mTheme);
+  return mTheme;
+}
+
+void nsPresContext::ThemeChanged(widget::ThemeChangeKind aKind) {
+  // NOTE(emilio): This ideally wouldn't need to be a _TEXT() marker, but
+  // otherwise the stack is not captured, see bug 1670046.
+  PROFILER_MARKER_TEXT("ThemeChanged", LAYOUT, MarkerStack::Capture(), ""_ns);
+
+  mPendingThemeChangeKind |= unsigned(aKind);
+
+  if (!mPendingThemeChanged) {
+    sLookAndFeelChanged = true;
+    sThemeChanged = true;
+
+    nsCOMPtr<nsIRunnable> ev =
+        NewRunnableMethod("nsPresContext::ThemeChangedInternal", this,
+                          &nsPresContext::ThemeChangedInternal);
+    nsresult rv = Document()->Dispatch(TaskCategory::Other, ev.forget());
+    if (NS_SUCCEEDED(rv)) {
+      mPendingThemeChanged = true;
+    }
+  }
+}
+
+void nsPresContext::ThemeChangedInternal() {
+  mPendingThemeChanged = false;
+
+  const auto kind = widget::ThemeChangeKind(mPendingThemeChangeKind);
+  mPendingThemeChangeKind = 0;
+
+  // Tell the theme that it changed, so it can flush any handles to stale theme
+  // data.
+  if (mTheme && sThemeChanged) {
+    mTheme->ThemeChanged();
+    sThemeChanged = false;
+  }
+
+  if (sLookAndFeelChanged) {
+    // Clear all cached LookAndFeel colors.
+    LookAndFeel::Refresh();
+    sLookAndFeelChanged = false;
+
+    // Vector images (SVG) may be using theme colors so we discard all cached
+    // surfaces. (We could add a vector image only version of DiscardAll, but
+    // in bug 940625 we decided theme changes are rare enough not to bother.)
+    image::SurfaceCacheUtils::DiscardAll();
+
+    if (XRE_IsParentProcess()) {
+      ContentParent::BroadcastThemeUpdate(kind);
+    }
+  }
+
+  // This will force the system metrics to be generated the next time they're
+  // used.
+  nsMediaFeatures::FreeSystemMetrics();
+
+  // Reset default background and foreground colors for the document since they
+  // may be using system colors.
+  PreferenceSheet::Refresh();
+
+  // Changes to system metrics and other look and feel values can change media
+  // queries on them.
+  //
+  // Changes in theme can change system colors (whose changes are properly
+  // reflected in computed style data), system fonts (whose changes are
+  // some reflected (like sizes and such) and some not), and -moz-appearance
+  // (whose changes are not), so we need to recascade for the first, and reflow
+  // for the rest.
+  auto restyleHint = (kind & widget::ThemeChangeKind::Style)
+                         ? RestyleHint::RecascadeSubtree()
+                         : RestyleHint{0};
+  auto changeHint = (kind & widget::ThemeChangeKind::Layout)
+                        ? NS_STYLE_HINT_REFLOW
+                        : nsChangeHint(0);
+  MediaFeatureValuesChanged(
+      {restyleHint, changeHint, MediaFeatureChangeReason::SystemMetricsChange},
+      MediaFeatureChangePropagation::All);
+}
+
+void nsPresContext::UIResolutionChanged() {
+  if (!mPendingUIResolutionChanged) {
+    nsCOMPtr<nsIRunnable> ev =
+        NewRunnableMethod("nsPresContext::UIResolutionChangedInternal", this,
+                          &nsPresContext::UIResolutionChangedInternal);
+    nsresult rv = Document()->Dispatch(TaskCategory::Other, ev.forget());
+    if (NS_SUCCEEDED(rv)) {
+      mPendingUIResolutionChanged = true;
+    }
+  }
+}
+
+void nsPresContext::UIResolutionChangedSync() {
+  if (!mPendingUIResolutionChanged) {
+    mPendingUIResolutionChanged = true;
+    UIResolutionChangedInternalScale(0.0);
+  }
+}
+
+static void NotifyTabUIResolutionChanged(nsIRemoteTab* aTab, void* aArg) {
+  aTab->NotifyResolutionChanged();
+}
+
+static void NotifyChildrenUIResolutionChanged(nsPIDOMWindowOuter* aWindow) {
+  nsCOMPtr<Document> doc = aWindow->GetExtantDoc();
+  RefPtr<nsPIWindowRoot> topLevelWin = nsContentUtils::GetWindowRoot(doc);
+  if (!topLevelWin) {
+    return;
+  }
+  topLevelWin->EnumerateBrowsers(NotifyTabUIResolutionChanged, nullptr);
+}
+
+void nsPresContext::UIResolutionChangedInternal() {
+  UIResolutionChangedInternalScale(0.0);
+}
+
+void nsPresContext::UIResolutionChangedInternalScale(double aScale) {
+  mPendingUIResolutionChanged = false;
+
+  mDeviceContext->CheckDPIChange(&aScale);
+  if (mCurAppUnitsPerDevPixel != mDeviceContext->AppUnitsPerDevPixel()) {
+    AppUnitsPerDevPixelChanged();
+  }
+
+  // Recursively notify all remote leaf descendants of the change.
+  if (nsPIDOMWindowOuter* window = mDocument->GetWindow()) {
+    NotifyChildrenUIResolutionChanged(window);
+  }
+
+  auto recurse = [aScale](dom::Document& aSubDoc) {
+    if (nsPresContext* pc = aSubDoc.GetPresContext()) {
+      // For subdocuments, we want to apply the parent's scale, because there
+      // are cases where the subdoc's device context is connected to a widget
+      // that has an out-of-date resolution (it's on a different screen, but
+      // currently hidden, and will not be updated until shown): bug 1249279.
+      pc->UIResolutionChangedInternalScale(aScale);
+    }
+    return CallState::Continue;
+  };
+  mDocument->EnumerateSubDocuments(recurse);
+}
+
+void nsPresContext::EmulateMedium(nsAtom* aMediaType) {
+  MOZ_ASSERT(!aMediaType || aMediaType->IsAsciiLowercase());
+  RefPtr<const nsAtom> oldMedium = Medium();
+  mMediaEmulationData.mMedium = aMediaType;
+
+  if (Medium() != oldMedium) {
+    MediaFeatureValuesChanged({MediaFeatureChangeReason::MediumChange},
+                              MediaFeatureChangePropagation::JustThisDocument);
+  }
+}
+
+void nsPresContext::ContentLanguageChanged() {
+  PostRebuildAllStyleDataEvent(nsChangeHint(0),
+                               RestyleHint::RecascadeSubtree());
+}
+
+bool nsPresContext::RegisterOneShotPostRefreshObserver(
+    mozilla::OneShotPostRefreshObserver* aObserver) {
+  RefreshDriver()->AddPostRefreshObserver(
+      static_cast<nsAPostRefreshObserver*>(aObserver));
+  mOneShotPostRefreshObservers.AppendElement(aObserver);
+  return true;
+}
+
+void nsPresContext::UnregisterOneShotPostRefreshObserver(
+    mozilla::OneShotPostRefreshObserver* aObserver) {
+  RefreshDriver()->RemovePostRefreshObserver(
+      static_cast<nsAPostRefreshObserver*>(aObserver));
+  DebugOnly<bool> removed =
+      mOneShotPostRefreshObservers.RemoveElement(aObserver);
+  MOZ_ASSERT(removed,
+             "OneShotPostRefreshObserver should be owned by PresContext");
+}
+
+void nsPresContext::ClearOneShotPostRefreshObservers() {
+  for (const auto& observer : mOneShotPostRefreshObservers) {
+    RefreshDriver()->RemovePostRefreshObserver(
+        static_cast<nsAPostRefreshObserver*>(observer));
+  }
+
+  mOneShotPostRefreshObservers.Clear();
+}
+
+void nsPresContext::RebuildAllStyleData(nsChangeHint aExtraHint,
+                                        const RestyleHint& aRestyleHint) {
+  if (!mPresShell) {
+    // We must have been torn down. Nothing to do here.
+    return;
+  }
+
+  // TODO(emilio): It's unclear to me why would these three calls below be
+  // needed. In particular, RebuildAllStyleData doesn't rebuild rules or
+  // specified style information and such (note the comment in
+  // RestyleManager::RebuildAllStyleData re. the funny semantics), so I
+  // don't know why should we rebuild the user font set / counter styles /
+  // etc...
+  mDocument->MarkUserFontSetDirty();
+  MarkCounterStylesDirty();
+  MarkFontFeatureValuesDirty();
+  PostRebuildAllStyleDataEvent(aExtraHint, aRestyleHint);
+}
+
+void nsPresContext::PostRebuildAllStyleDataEvent(
+    nsChangeHint aExtraHint, const RestyleHint& aRestyleHint) {
+  if (!mPresShell) {
+    // We must have been torn down. Nothing to do here.
+    return;
+  }
+  if (aRestyleHint.DefinitelyRecascadesAllSubtree()) {
+    mUsesExChUnits = false;
+  }
+  RestyleManager()->RebuildAllStyleData(aExtraHint, aRestyleHint);
+}
+
+void nsPresContext::MediaFeatureValuesChanged(
+    const MediaFeatureChange& aChange,
+    MediaFeatureChangePropagation aPropagation) {
+  if (mPresShell) {
+    mPresShell->EnsureStyleFlush();
+  }
+
+  if (!mPendingMediaFeatureValuesChange) {
+    mPendingMediaFeatureValuesChange = MakeUnique<MediaFeatureChange>(aChange);
+  } else {
+    *mPendingMediaFeatureValuesChange |= aChange;
+  }
+
+  if (aPropagation & MediaFeatureChangePropagation::Images) {
+    // Propagate the media feature value change down to any SVG images the
+    // document is using.
+    mDocument->ImageTracker()->MediaFeatureValuesChangedAllDocuments(aChange);
+  }
+
+  if (aPropagation & MediaFeatureChangePropagation::SubDocuments) {
+    // And then into any subdocuments.
+    auto recurse = [&aChange, aPropagation](dom::Document& aSubDoc) {
+      if (nsPresContext* pc = aSubDoc.GetPresContext()) {
+        pc->MediaFeatureValuesChanged(aChange, aPropagation);
+      }
+      return CallState::Continue;
+    };
+    mDocument->EnumerateSubDocuments(recurse);
+  }
+}
+
+bool nsPresContext::FlushPendingMediaFeatureValuesChanged() {
+  if (!mPendingMediaFeatureValuesChange) {
+    return false;
+  }
+
+  MediaFeatureChange change = *mPendingMediaFeatureValuesChange;
+  mPendingMediaFeatureValuesChange.reset();
+
+  // MediumFeaturesChanged updates the applied rules, so it always gets called.
+  if (mPresShell) {
+    change.mRestyleHint |=
+        mPresShell->StyleSet()->MediumFeaturesChanged(change.mReason);
+  }
+
+  const bool changedStyle = change.mRestyleHint || change.mChangeHint;
+  if (changedStyle) {
+    RebuildAllStyleData(change.mChangeHint, change.mRestyleHint);
+  }
+
+  if (mDocument->IsBeingUsedAsImage()) {
+    MOZ_ASSERT(mDocument->MediaQueryLists().isEmpty());
+    return changedStyle;
+  }
+
+  mDocument->NotifyMediaFeatureValuesChanged();
+
+  // https://drafts.csswg.org/cssom-view/#evaluate-media-queries-and-report-changes
+  //
+  // Media query list listeners should be notified from a queued task
+  // (in HTML5 terms), although we also want to notify them on certain
+  // flushes.  (We're already running off an event.)
+  //
+  // TODO: This should be better integrated into the "update the rendering"
+  // steps: https://html.spec.whatwg.org/#update-the-rendering
+  //
+  // Note that we do this after the new style from media queries in
+  // style sheets has been computed.
+
+  if (mDocument->MediaQueryLists().isEmpty()) {
+    return changedStyle;
+  }
+
+  // We build a list of all the notifications we're going to send
+  // before we send any of them.
+  nsTArray<RefPtr<mozilla::dom::MediaQueryList>> listsToNotify;
+  for (MediaQueryList* mql = mDocument->MediaQueryLists().getFirst(); mql;
+       mql = static_cast<LinkedListElement<MediaQueryList>*>(mql)->getNext()) {
+    if (mql->MediaFeatureValuesChanged()) {
+      listsToNotify.AppendElement(mql);
+    }
+  }
+
+  if (!listsToNotify.IsEmpty()) {
+    nsContentUtils::AddScriptRunner(NS_NewRunnableFunction(
+        "nsPresContext::FlushPendingMediaFeatureValuesChanged",
+        [list = std::move(listsToNotify)] {
+          for (const auto& mql : list) {
+            nsAutoMicroTask mt;
+            mql->FireChangeEvent();
+          }
+        }));
+  }
+
+  return changedStyle;
+}
+
+void nsPresContext::SizeModeChanged(nsSizeMode aSizeMode) {
+  if (nsPIDOMWindowOuter* window = mDocument->GetWindow()) {
+    nsContentUtils::CallOnAllRemoteChildren(
+        window, [&aSizeMode](BrowserParent* aBrowserParent) -> CallState {
+          aBrowserParent->SizeModeChanged(aSizeMode);
+          return CallState::Continue;
+        });
+  }
+  MediaFeatureValuesChanged({MediaFeatureChangeReason::SizeModeChange},
+                            MediaFeatureChangePropagation::SubDocuments);
+}
+
+nsCompatibility nsPresContext::CompatibilityMode() const {
+  return Document()->GetCompatibilityMode();
+}
+
+void nsPresContext::SetPaginatedScrolling(bool aPaginated) {
+  if (mType == eContext_PrintPreview || mType == eContext_PageLayout)
+    mCanPaginatedScroll = aPaginated;
+}
+
+void nsPresContext::SetPrintSettings(nsIPrintSettings* aPrintSettings) {
+  if (mMedium != nsGkAtoms::print) {
+    return;
+  }
+
+  mPrintSettings = aPrintSettings;
+  mDefaultPageMargin = nsMargin();
+  if (!mPrintSettings) {
+    return;
+  }
+
+  // set the presentation context to the value in the print settings
+  mDrawColorBackground = mPrintSettings->GetPrintBGColors();
+  mDrawImageBackground = mPrintSettings->GetPrintBGImages();
+
+  nsIntMargin unwriteableTwips = mPrintSettings->GetUnwriteableMarginInTwips();
+  NS_ASSERTION(unwriteableTwips.top >= 0 && unwriteableTwips.right >= 0 &&
+                   unwriteableTwips.bottom >= 0 && unwriteableTwips.left >= 0,
+               "Unwriteable twips should be non-negative");
+
+  nsIntMargin marginTwips = mPrintSettings->GetMarginInTwips();
+  marginTwips.EnsureAtLeast(unwriteableTwips);
+  mDefaultPageMargin = nsPresContext::CSSTwipsToAppUnits(marginTwips);
+}
+
+bool nsPresContext::EnsureVisible() {
+  nsCOMPtr<nsIDocShell> docShell(GetDocShell());
+  if (!docShell) {
+    return false;
+  }
+  nsCOMPtr<nsIContentViewer> cv;
+  docShell->GetContentViewer(getter_AddRefs(cv));
+  // Make sure this is the content viewer we belong with
+  if (!cv || cv->GetPresContext() != this) {
+    return false;
+  }
+  // OK, this is us.  We want to call Show() on the content viewer.
+  nsresult result = cv->Show();
+  return NS_SUCCEEDED(result);
+}
+
+#ifdef MOZ_REFLOW_PERF
+void nsPresContext::CountReflows(const char* aName, nsIFrame* aFrame) {
+  if (mPresShell) {
+    mPresShell->CountReflows(aName, aFrame);
+  }
+}
+#endif
+
+bool nsPresContext::HasAuthorSpecifiedRules(const nsIFrame* aFrame,
+                                            uint32_t aRuleTypeMask) const {
+  const bool padding = aRuleTypeMask & NS_AUTHOR_SPECIFIED_PADDING;
+  const bool borderBackground =
+      aRuleTypeMask & NS_AUTHOR_SPECIFIED_BORDER_OR_BACKGROUND;
+  const auto& style = *aFrame->Style();
+
+  if (padding && style.HasAuthorSpecifiedPadding()) {
+    return true;
+  }
+
+  if (borderBackground && style.HasAuthorSpecifiedBorderOrBackground()) {
+    return true;
+  }
+
+  return false;
+}
+
+gfxUserFontSet* nsPresContext::GetUserFontSet() {
+  return mDocument->GetUserFontSet();
+}
+
+void nsPresContext::UserFontSetUpdated(gfxUserFontEntry* aUpdatedFont) {
+  if (!mPresShell) {
+    return;
+  }
+
+  // Note: this method is called without a font when rules in the userfont set
+  // are updated.
+  //
+  // We can avoid a full restyle if font-metric-dependent units are not in use,
+  // since we know there's no style resolution that would depend on this font
+  // and trigger its load.
+  //
+  // TODO(emilio): We could be more granular if we knew which families have
+  // potentially changed.
+  if (!aUpdatedFont) {
+    auto hint =
+        UsesExChUnits() ? RestyleHint::RecascadeSubtree() : RestyleHint{0};
+    PostRebuildAllStyleDataEvent(NS_STYLE_HINT_REFLOW, hint);
+    return;
+  }
+
+  // Iterate over the frame tree looking for frames associated with the
+  // downloadable font family in question. If a frame's nsStyleFont has
+  // the name, check the font group associated with the metrics to see if
+  // it contains that specific font (i.e. the one chosen within the family
+  // given the weight, width, and slant from the nsStyleFont). If it does,
+  // mark that frame dirty and skip inspecting its descendants.
+  if (nsIFrame* root = mPresShell->GetRootFrame()) {
+    nsFontFaceUtils::MarkDirtyForFontChange(root, aUpdatedFont);
+  }
+}
+
+class CounterStyleCleaner final : public nsAPostRefreshObserver {
+ public:
+  CounterStyleCleaner(nsRefreshDriver* aRefreshDriver,
+                      CounterStyleManager* aCounterStyleManager)
+      : mRefreshDriver(aRefreshDriver),
+        mCounterStyleManager(aCounterStyleManager) {}
+  virtual ~CounterStyleCleaner() = default;
+
+  void DidRefresh() final {
+    mRefreshDriver->RemovePostRefreshObserver(this);
+    mCounterStyleManager->CleanRetiredStyles();
+    delete this;
+  }
+
+ private:
+  RefPtr<nsRefreshDriver> mRefreshDriver;
+  RefPtr<CounterStyleManager> mCounterStyleManager;
+};
+
+void nsPresContext::FlushCounterStyles() {
+  if (!mPresShell) {
+    return;  // we've been torn down
+  }
+  if (mCounterStyleManager->IsInitial()) {
+    // Still in its initial state, no need to clean.
+    return;
+  }
+
+  if (mCounterStylesDirty) {
+    bool changed = mCounterStyleManager->NotifyRuleChanged();
+    if (changed) {
+      PresShell()->NotifyCounterStylesAreDirty();
+      PostRebuildAllStyleDataEvent(NS_STYLE_HINT_REFLOW, RestyleHint{0});
+      RefreshDriver()->AddPostRefreshObserver(
+          new CounterStyleCleaner(RefreshDriver(), mCounterStyleManager));
+    }
+    mCounterStylesDirty = false;
+  }
+}
+
+void nsPresContext::MarkCounterStylesDirty() {
+  if (mCounterStyleManager->IsInitial()) {
+    // Still in its initial state, no need to touch anything.
+    return;
+  }
+
+  mCounterStylesDirty = true;
+}
+
+void nsPresContext::NotifyMissingFonts() {
+  if (mMissingFonts) {
+    mMissingFonts->Flush();
+  }
+}
+
+void nsPresContext::EnsureSafeToHandOutCSSRules() {
+  if (!mPresShell->StyleSet()->EnsureUniqueInnerOnCSSSheets()) {
+    // Nothing to do.
+    return;
+  }
+
+  RebuildAllStyleData(nsChangeHint(0), RestyleHint::RestyleSubtree());
+}
+
+void nsPresContext::FireDOMPaintEvent(
+    nsTArray<nsRect>* aList, TransactionId aTransactionId,
+    mozilla::TimeStamp aTimeStamp /* = mozilla::TimeStamp() */) {
+  nsPIDOMWindowInner* ourWindow = mDocument->GetInnerWindow();
+  if (!ourWindow) return;
+
+  nsCOMPtr<EventTarget> dispatchTarget = do_QueryInterface(ourWindow);
+  nsCOMPtr<EventTarget> eventTarget = dispatchTarget;
+  if (!IsChrome() && !mSendAfterPaintToContent) {
+    // Don't tell the window about this event, it should not know that
+    // something happened in a subdocument. Tell only the chrome event handler.
+    // (Events sent to the window get propagated to the chrome event handler
+    // automatically.)
+    dispatchTarget = ourWindow->GetParentTarget();
+    if (!dispatchTarget) {
+      return;
+    }
+  }
+
+  if (aTimeStamp.IsNull()) {
+    aTimeStamp = mozilla::TimeStamp::Now();
+  }
+  DOMHighResTimeStamp timeStamp = 0;
+  if (ourWindow) {
+    mozilla::dom::Performance* perf = ourWindow->GetPerformance();
+    if (perf) {
+      timeStamp = perf->GetDOMTiming()->TimeStampToDOMHighRes(aTimeStamp);
+    }
+  }
+
+  // Events sent to the window get propagated to the chrome event handler
+  // automatically.
+  //
+  // This will empty our list in case dispatching the event causes more damage
+  // (hopefully it won't, or we're likely to get an infinite loop! At least
+  // it won't be blocking app execution though).
+  RefPtr<NotifyPaintEvent> event =
+      NS_NewDOMNotifyPaintEvent(eventTarget, this, nullptr, eAfterPaint, aList,
+                                uint64_t(aTransactionId), timeStamp);
+
+  // Even if we're not telling the window about the event (so eventTarget is
+  // the chrome event handler, not the window), the window is still
+  // logically the event target.
+  event->SetTarget(eventTarget);
+  event->SetTrusted(true);
+  EventDispatcher::DispatchDOMEvent(dispatchTarget, nullptr,
+                                    static_cast<Event*>(event), this, nullptr);
+}
+
+static bool MayHavePaintEventListener(nsPIDOMWindowInner* aInnerWindow) {
+  if (!aInnerWindow) return false;
+  if (aInnerWindow->HasPaintEventListeners()) return true;
+
+  EventTarget* parentTarget = aInnerWindow->GetParentTarget();
+  if (!parentTarget) return false;
+
+  EventListenerManager* manager = nullptr;
+  if ((manager = parentTarget->GetExistingListenerManager()) &&
+      manager->MayHavePaintEventListener()) {
+    return true;
+  }
+
+  nsCOMPtr<nsINode> node;
+  if (parentTarget != aInnerWindow->GetChromeEventHandler()) {
+    nsCOMPtr<nsIInProcessContentFrameMessageManager> mm =
+        do_QueryInterface(parentTarget);
+    if (mm) {
+      node = mm->GetOwnerContent();
+    }
+  }
+
+  if (!node) {
+    node = do_QueryInterface(parentTarget);
+  }
+  if (node)
+    return MayHavePaintEventListener(node->OwnerDoc()->GetInnerWindow());
+
+  nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(parentTarget);
+  if (window) return MayHavePaintEventListener(window);
+
+  nsCOMPtr<nsPIWindowRoot> root = do_QueryInterface(parentTarget);
+  EventTarget* browserChildGlobal;
+  return root && (browserChildGlobal = root->GetParentTarget()) &&
+         (manager = browserChildGlobal->GetExistingListenerManager()) &&
+         manager->MayHavePaintEventListener();
+}
+
+bool nsPresContext::MayHavePaintEventListener() {
+  return ::MayHavePaintEventListener(mDocument->GetInnerWindow());
+}
+
+bool nsPresContext::MayHavePaintEventListenerInSubDocument() {
+  if (MayHavePaintEventListener()) {
+    return true;
+  }
+
+  bool result = false;
+  auto recurse = [&result](dom::Document& aSubDoc) {
+    if (nsPresContext* pc = aSubDoc.GetPresContext()) {
+      if (pc->MayHavePaintEventListenerInSubDocument()) {
+        result = true;
+        return CallState::Stop;
+      }
+    }
+    return CallState::Continue;
+  };
+
+  mDocument->EnumerateSubDocuments(recurse);
+  return result;
+}
+
+void nsPresContext::NotifyInvalidation(TransactionId aTransactionId,
+                                       const nsIntRect& aRect) {
+  // Prevent values from overflow after DevPixelsToAppUnits().
+  //
+  // DevPixelsTopAppUnits() will multiple a factor (60) to the value,
+  // it may make the result value over the edge (overflow) of max or
+  // min value of int32_t. Compute the max sized dev pixel rect that
+  // we can support and intersect with it.
+  nsIntRect clampedRect = nsIntRect::MaxIntRect();
+  clampedRect.ScaleInverseRoundIn(AppUnitsPerDevPixel());
+
+  clampedRect = clampedRect.Intersect(aRect);
+
+  nsRect rect(DevPixelsToAppUnits(clampedRect.x),
+              DevPixelsToAppUnits(clampedRect.y),
+              DevPixelsToAppUnits(clampedRect.width),
+              DevPixelsToAppUnits(clampedRect.height));
+  NotifyInvalidation(aTransactionId, rect);
+}
+
+nsPresContext::TransactionInvalidations* nsPresContext::GetInvalidations(
+    TransactionId aTransactionId) {
+  for (TransactionInvalidations& t : mTransactions) {
+    if (t.mTransactionId == aTransactionId) {
+      return &t;
+    }
+  }
+  return nullptr;
+}
+
+void nsPresContext::NotifyInvalidation(TransactionId aTransactionId,
+                                       const nsRect& aRect) {
+  MOZ_ASSERT(GetContainerWeak(), "Invalidation in detached pres context");
+
+  // If there is no paint event listener, then we don't need to fire
+  // the asynchronous event. We don't even need to record invalidation.
+  // MayHavePaintEventListener is pretty cheap and we could make it
+  // even cheaper by providing a more efficient
+  // nsPIDOMWindow::GetListenerManager.
+
+  nsPresContext* pc;
+  for (pc = this; pc; pc = pc->GetParentPresContext()) {
+    TransactionInvalidations* transaction =
+        pc->GetInvalidations(aTransactionId);
+    if (transaction) {
+      break;
+    } else {
+      transaction = pc->mTransactions.AppendElement();
+      transaction->mTransactionId = aTransactionId;
+    }
+  }
+
+  TransactionInvalidations* transaction = GetInvalidations(aTransactionId);
+  MOZ_ASSERT(transaction);
+  transaction->mInvalidations.AppendElement(aRect);
+}
+
+/* static */
+void nsPresContext::NotifySubDocInvalidation(ContainerLayer* aContainer,
+                                             const nsIntRegion* aRegion) {
+  ContainerLayerPresContext* data = static_cast<ContainerLayerPresContext*>(
+      aContainer->GetUserData(&gNotifySubDocInvalidationData));
+  if (!data) {
+    return;
+  }
+
+  TransactionId transactionId = aContainer->Manager()->GetLastTransactionId();
+  IntRect visibleBounds =
+      aContainer->GetVisibleRegion().GetBounds().ToUnknownRect();
+
+  if (!aRegion) {
+    IntRect rect(IntPoint(0, 0), visibleBounds.Size());
+    data->mPresContext->NotifyInvalidation(transactionId, rect);
+    return;
+  }
+
+  nsIntPoint topLeft = visibleBounds.TopLeft();
+  for (auto iter = aRegion->RectIter(); !iter.Done(); iter.Next()) {
+    nsIntRect rect(iter.Get());
+    // PresContext coordinate space is relative to the start of our visible
+    // region. Is this really true? This feels like the wrong way to get the
+    // right answer.
+    rect.MoveBy(-topLeft);
+    data->mPresContext->NotifyInvalidation(transactionId, rect);
+  }
+}
+
+void nsPresContext::SetNotifySubDocInvalidationData(
+    ContainerLayer* aContainer) {
+  ContainerLayerPresContext* pres = new ContainerLayerPresContext;
+  pres->mPresContext = this;
+  aContainer->SetUserData(&gNotifySubDocInvalidationData, pres);
+}
+
+/* static */
+void nsPresContext::ClearNotifySubDocInvalidationData(
+    ContainerLayer* aContainer) {
+  aContainer->SetUserData(&gNotifySubDocInvalidationData, nullptr);
+}
+
+class DelayedFireDOMPaintEvent : public Runnable {
+ public:
+  DelayedFireDOMPaintEvent(
+      nsPresContext* aPresContext, nsTArray<nsRect>&& aList,
+      TransactionId aTransactionId,
+      const mozilla::TimeStamp& aTimeStamp = mozilla::TimeStamp())
+      : mozilla::Runnable("DelayedFireDOMPaintEvent"),
+        mPresContext(aPresContext),
+        mTransactionId(aTransactionId),
+        mTimeStamp(aTimeStamp),
+        mList(std::move(aList)) {
+    MOZ_ASSERT(mPresContext->GetContainerWeak(),
+               "DOMPaintEvent requested for a detached pres context");
+  }
+  NS_IMETHOD Run() override {
+    // The pres context might have been detached during the delay -
+    // that's fine, just don't fire the event.
+    if (mPresContext->GetContainerWeak()) {
+      mPresContext->FireDOMPaintEvent(&mList, mTransactionId, mTimeStamp);
+    }
+    return NS_OK;
+  }
+
+  RefPtr<nsPresContext> mPresContext;
+  TransactionId mTransactionId;
+  const mozilla::TimeStamp mTimeStamp;
+  nsTArray<nsRect> mList;
+};
+
+void nsPresContext::NotifyRevokingDidPaint(TransactionId aTransactionId) {
+  if ((IsRoot() || !PresShell()->IsVisible()) && mTransactions.IsEmpty()) {
+    return;
+  }
+
+  TransactionInvalidations* transaction = nullptr;
+  for (auto& t : mTransactions) {
+    if (t.mTransactionId == aTransactionId) {
+      transaction = &t;
+      break;
+    }
+  }
+  // If there are no transaction invalidations (which imply callers waiting
+  // on the event) for this revoked id, then we don't need to fire a
+  // MozAfterPaint.
+  if (!transaction) {
+    return;
+  }
+
+  // If there are queued transactions with an earlier id, we can't send
+  // our event now since it will arrive out of order. Set the waiting for
+  // previous transaction flag to true, and we'll send the event when
+  // the others are completed.
+  // If this is the only transaction, then we can send it immediately.
+  if (mTransactions.Length() == 1) {
+    nsCOMPtr<nsIRunnable> ev = new DelayedFireDOMPaintEvent(
+        this, std::move(transaction->mInvalidations),
+        transaction->mTransactionId, mozilla::TimeStamp());
+    nsContentUtils::AddScriptRunner(ev);
+    mTransactions.RemoveElementAt(0);
+  } else {
+    transaction->mIsWaitingForPreviousTransaction = true;
+  }
+
+  auto recurse = [&aTransactionId](dom::Document& aSubDoc) {
+    if (nsPresContext* pc = aSubDoc.GetPresContext()) {
+      pc->NotifyRevokingDidPaint(aTransactionId);
+    }
+    return CallState::Continue;
+  };
+  mDocument->EnumerateSubDocuments(recurse);
+}
+
+void nsPresContext::NotifyDidPaintForSubtree(
+    TransactionId aTransactionId, const mozilla::TimeStamp& aTimeStamp) {
+  if (mFirstContentfulPaintTransactionId && !mHadContentfulPaintComposite) {
+    if (aTransactionId >= *mFirstContentfulPaintTransactionId) {
+      mHadContentfulPaintComposite = true;
+      RefPtr<nsDOMNavigationTiming> timing = mDocument->GetNavigationTiming();
+      if (timing && !IsPrintingOrPrintPreview()) {
+        timing->NotifyContentfulPaintForRootContentDocument(aTimeStamp);
+      }
+    }
+  }
+
+  if (IsRoot() && mTransactions.IsEmpty()) {
+    return;
+  }
+
+  if (!PresShell()->IsVisible() && mTransactions.IsEmpty()) {
+    return;
+  }
+
+  // Non-root prescontexts fire MozAfterPaint to all their descendants
+  // unconditionally, even if no invalidations have been collected. This is
+  // because we don't want to eat the cost of collecting invalidations for
+  // every subdocument (which would require putting every subdocument in its
+  // own layer).
+
+  bool sent = false;
+  uint32_t i = 0;
+  while (i < mTransactions.Length()) {
+    if (mTransactions[i].mTransactionId <= aTransactionId) {
+      if (!mTransactions[i].mInvalidations.IsEmpty()) {
+        nsCOMPtr<nsIRunnable> ev = new DelayedFireDOMPaintEvent(
+            this, std::move(mTransactions[i].mInvalidations),
+            mTransactions[i].mTransactionId, aTimeStamp);
+        nsContentUtils::AddScriptRunner(ev);
+        sent = true;
+      }
+      mTransactions.RemoveElementAt(i);
+    } else {
+      // If there are transaction which is waiting for this transaction,
+      // we should fire a MozAfterPaint immediately.
+      if (sent && mTransactions[i].mIsWaitingForPreviousTransaction) {
+        nsCOMPtr<nsIRunnable> ev = new DelayedFireDOMPaintEvent(
+            this, std::move(mTransactions[i].mInvalidations),
+            mTransactions[i].mTransactionId, aTimeStamp);
+        nsContentUtils::AddScriptRunner(ev);
+        sent = true;
+        mTransactions.RemoveElementAt(i);
+        continue;
+      }
+      i++;
+    }
+  }
+
+  if (!sent) {
+    nsTArray<nsRect> dummy;
+    nsCOMPtr<nsIRunnable> ev = new DelayedFireDOMPaintEvent(
+        this, std::move(dummy), aTransactionId, aTimeStamp);
+    nsContentUtils::AddScriptRunner(ev);
+  }
+
+  auto recurse = [&aTransactionId, &aTimeStamp](dom::Document& aSubDoc) {
+    if (nsPresContext* pc = aSubDoc.GetPresContext()) {
+      pc->NotifyDidPaintForSubtree(aTransactionId, aTimeStamp);
+    }
+    return CallState::Continue;
+  };
+  mDocument->EnumerateSubDocuments(recurse);
+}
+
+already_AddRefed<nsITimer> nsPresContext::CreateTimer(
+    nsTimerCallbackFunc aCallback, const char* aName, uint32_t aDelay) {
+  nsCOMPtr<nsITimer> timer;
+  NS_NewTimerWithFuncCallback(getter_AddRefs(timer), aCallback, this, aDelay,
+                              nsITimer::TYPE_ONE_SHOT, aName,
+                              Document()->EventTargetFor(TaskCategory::Other));
+  return timer.forget();
+}
+
+static bool sGotInterruptEnv = false;
+enum InterruptMode { ModeRandom, ModeCounter, ModeEvent };
+// Controlled by the GECKO_REFLOW_INTERRUPT_MODE env var; allowed values are
+// "random" (except on Windows) or "counter".  If neither is used, the mode is
+// ModeEvent.
+static InterruptMode sInterruptMode = ModeEvent;
+#ifndef XP_WIN
+// Used for the "random" mode.  Controlled by the GECKO_REFLOW_INTERRUPT_SEED
+// env var.
+static uint32_t sInterruptSeed = 1;
+#endif
+// Used for the "counter" mode.  This is the number of unskipped interrupt
+// checks that have to happen before we interrupt.  Controlled by the
+// GECKO_REFLOW_INTERRUPT_FREQUENCY env var.
+static uint32_t sInterruptMaxCounter = 10;
+// Used for the "counter" mode.  This counts up to sInterruptMaxCounter and is
+// then reset to 0.
+static uint32_t sInterruptCounter;
+// Number of interrupt checks to skip before really trying to interrupt.
+// Controlled by the GECKO_REFLOW_INTERRUPT_CHECKS_TO_SKIP env var.
+static uint32_t sInterruptChecksToSkip = 200;
+// Number of milliseconds that a reflow should be allowed to run for before we
+// actually allow interruption.  Controlled by the
+// GECKO_REFLOW_MIN_NOINTERRUPT_DURATION env var.  Can't be initialized here,
+// because TimeDuration/TimeStamp is not safe to use in static constructors..
+static TimeDuration sInterruptTimeout;
+
+static void GetInterruptEnv() {
+  char* ev = PR_GetEnv("GECKO_REFLOW_INTERRUPT_MODE");
+  if (ev) {
+#ifndef XP_WIN
+    if (PL_strcasecmp(ev, "random") == 0) {
+      ev = PR_GetEnv("GECKO_REFLOW_INTERRUPT_SEED");
+      if (ev) {
+        sInterruptSeed = atoi(ev);
+      }
+      srandom(sInterruptSeed);
+      sInterruptMode = ModeRandom;
+    } else
+#endif
+        if (PL_strcasecmp(ev, "counter") == 0) {
+      ev = PR_GetEnv("GECKO_REFLOW_INTERRUPT_FREQUENCY");
+      if (ev) {
+        sInterruptMaxCounter = atoi(ev);
+      }
+      sInterruptCounter = 0;
+      sInterruptMode = ModeCounter;
+    }
+  }
+  ev = PR_GetEnv("GECKO_REFLOW_INTERRUPT_CHECKS_TO_SKIP");
+  if (ev) {
+    sInterruptChecksToSkip = atoi(ev);
+  }
+
+  ev = PR_GetEnv("GECKO_REFLOW_MIN_NOINTERRUPT_DURATION");
+  int duration_ms = ev ? atoi(ev) : 100;
+  sInterruptTimeout = TimeDuration::FromMilliseconds(duration_ms);
+}
+
+bool nsPresContext::HavePendingInputEvent() {
+  switch (sInterruptMode) {
+#ifndef XP_WIN
+    case ModeRandom:
+      return (random() & 1);
+#endif
+    case ModeCounter:
+      if (sInterruptCounter < sInterruptMaxCounter) {
+        ++sInterruptCounter;
+        return false;
+      }
+      sInterruptCounter = 0;
+      return true;
+    default:
+    case ModeEvent: {
+      nsIFrame* f = PresShell()->GetRootFrame();
+      if (f) {
+        nsIWidget* w = f->GetNearestWidget();
+        if (w) {
+          return w->HasPendingInputEvent();
+        }
+      }
+      return false;
+    }
+  }
+}
+
+bool nsPresContext::HasPendingRestyleOrReflow() {
+  mozilla::PresShell* presShell = PresShell();
+  return presShell->NeedStyleFlush() || presShell->HasPendingReflow();
+}
+
+void nsPresContext::ReflowStarted(bool aInterruptible) {
+#ifdef NOISY_INTERRUPTIBLE_REFLOW
+  if (!aInterruptible) {
+    printf("STARTING NONINTERRUPTIBLE REFLOW\n");
+  }
+#endif
+  // We don't support interrupting in paginated contexts, since page
+  // sequences only handle initial reflow
+  mInterruptsEnabled = aInterruptible && !IsPaginated() &&
+                       StaticPrefs::layout_interruptible_reflow_enabled();
+
+  // Don't set mHasPendingInterrupt based on HavePendingInputEvent() here.  If
+  // we ever change that, then we need to update the code in
+  // PresShell::DoReflow to only add the just-reflown root to dirty roots if
+  // it's actually dirty.  Otherwise we can end up adding a root that has no
+  // interruptible descendants, just because we detected an interrupt at reflow
+  // start.
+  mHasPendingInterrupt = false;
+
+  mInterruptChecksToSkip = sInterruptChecksToSkip;
+
+  if (mInterruptsEnabled) {
+    mReflowStartTime = TimeStamp::Now();
+  }
+}
+
+bool nsPresContext::CheckForInterrupt(nsIFrame* aFrame) {
+  if (mHasPendingInterrupt) {
+    mPresShell->FrameNeedsToContinueReflow(aFrame);
+    return true;
+  }
+
+  if (!sGotInterruptEnv) {
+    sGotInterruptEnv = true;
+    GetInterruptEnv();
+  }
+
+  if (!mInterruptsEnabled) {
+    return false;
+  }
+
+  if (mInterruptChecksToSkip > 0) {
+    --mInterruptChecksToSkip;
+    return false;
+  }
+  mInterruptChecksToSkip = sInterruptChecksToSkip;
+
+  // Don't interrupt if it's been less than sInterruptTimeout since we started
+  // the reflow.
+  mHasPendingInterrupt =
+      TimeStamp::Now() - mReflowStartTime > sInterruptTimeout &&
+      HavePendingInputEvent() && !IsChrome();
+
+  if (mPendingInterruptFromTest) {
+    mPendingInterruptFromTest = false;
+    mHasPendingInterrupt = true;
+  }
+
+  if (mHasPendingInterrupt) {
+#ifdef NOISY_INTERRUPTIBLE_REFLOW
+    printf("*** DETECTED pending interrupt (time=%lld)\n", PR_Now());
+#endif /* NOISY_INTERRUPTIBLE_REFLOW */
+    mPresShell->FrameNeedsToContinueReflow(aFrame);
+  }
+  return mHasPendingInterrupt;
+}
+
+nsIFrame* nsPresContext::GetPrimaryFrameFor(nsIContent* aContent) {
+  MOZ_ASSERT(aContent, "Don't do that");
+  if (GetPresShell() &&
+      GetPresShell()->GetDocument() == aContent->GetComposedDoc()) {
+    return aContent->GetPrimaryFrame();
+  }
+  return nullptr;
+}
+
+size_t nsPresContext::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
+  // Measurement may be added later if DMD finds it is worthwhile.
+  return 0;
+}
+
+bool nsPresContext::IsRootContentDocument() const {
+  // Default to the in process version for now, but we should try
+  // to remove callers of this.
+  return IsRootContentDocumentInProcess();
+}
+
+bool nsPresContext::IsRootContentDocumentInProcess() const {
+  if (mDocument->IsResourceDoc()) {
+    return false;
+  }
+  if (IsChrome()) {
+    return false;
+  }
+  // We may not have a root frame, so use views.
+  nsView* view = PresShell()->GetViewManager()->GetRootView();
+  if (!view) {
+    return false;
+  }
+  view = view->GetParent();  // anonymous inner view
+  if (!view) {
+    return true;
+  }
+  view = view->GetParent();  // subdocumentframe's view
+  if (!view) {
+    return true;
+  }
+
+  nsIFrame* f = view->GetFrame();
+  return (f && f->PresContext()->IsChrome());
+}
+
+bool nsPresContext::IsRootContentDocumentCrossProcess() const {
+  if (mDocument->IsResourceDoc()) {
+    return false;
+  }
+
+  return mDocument->IsTopLevelContentDocument();
+}
+
+void nsPresContext::NotifyNonBlankPaint() {
+  MOZ_ASSERT(!mHadNonBlankPaint);
+  mHadNonBlankPaint = true;
+  if (IsRootContentDocument()) {
+    RefPtr<nsDOMNavigationTiming> timing = mDocument->GetNavigationTiming();
+    if (timing && !IsPrintingOrPrintPreview()) {
+      timing->NotifyNonBlankPaintForRootContentDocument();
+    }
+
+    mFirstNonBlankPaintTime = TimeStamp::Now();
+  }
+}
+
+void nsPresContext::NotifyContentfulPaint() {
+  if (!mHadContentfulPaint) {
+#if defined(MOZ_WIDGET_ANDROID)
+    (new AsyncEventDispatcher(mDocument, u"MozFirstContentfulPaint"_ns,
+                              CanBubble::eYes, ChromeOnlyDispatch::eYes))
+        ->PostDOMEvent();
+#endif
+    mHadContentfulPaint = true;
+    if (nsRootPresContext* rootPresContext = GetRootPresContext()) {
+      mFirstContentfulPaintTransactionId =
+          Some(rootPresContext->mRefreshDriver->LastTransactionId().Next());
+      if (nsPIDOMWindowInner* innerWindow = mDocument->GetInnerWindow()) {
+        if (Performance* perf = innerWindow->GetPerformance()) {
+          TimeStamp nowTime =
+              rootPresContext->RefreshDriver()->MostRecentRefresh(
+                  /* aEnsureTimerStarted */ false);
+          MOZ_ASSERT(
+              !nowTime.IsNull(),
+              "Most recent refresh timestamp should exist since we are in "
+              "a refresh driver tick");
+          MOZ_ASSERT(rootPresContext->RefreshDriver()->IsInRefresh(),
+                     "We should only notify contentful paint during refresh "
+                     "driver ticks");
+          RefPtr<PerformancePaintTiming> paintTiming =
+              new PerformancePaintTiming(perf, u"first-contentful-paint"_ns,
+                                         nowTime);
+          perf->SetFCPTimingEntry(paintTiming);
+        }
+      }
+    }
+  }
+}
+
+void nsPresContext::NotifyPaintStatusReset() {
+  mHadNonBlankPaint = false;
+  mHadContentfulPaint = false;
+#if defined(MOZ_WIDGET_ANDROID)
+  (new AsyncEventDispatcher(mDocument, u"MozPaintStatusReset"_ns,
+                            CanBubble::eYes, ChromeOnlyDispatch::eYes))
+      ->PostDOMEvent();
+#endif
+}
+
+void nsPresContext::NotifyDOMContentFlushed() {
+  NS_ENSURE_TRUE_VOID(mPresShell);
+  if (IsRootContentDocument()) {
+    RefPtr<nsDOMNavigationTiming> timing = mDocument->GetNavigationTiming();
+    if (timing) {
+      timing->NotifyDOMContentFlushedForRootContentDocument();
+    }
+  }
+}
+
+bool nsPresContext::GetPaintFlashing() const {
+  if (!mPaintFlashingInitialized) {
+    bool pref = Preferences::GetBool("nglayout.debug.paint_flashing");
+    if (!pref && IsChrome()) {
+      pref = Preferences::GetBool("nglayout.debug.paint_flashing_chrome");
+    }
+    mPaintFlashing = pref;
+    mPaintFlashingInitialized = true;
+  }
+  return mPaintFlashing;
+}
+
+nscoord nsPresContext::GfxUnitsToAppUnits(gfxFloat aGfxUnits) const {
+  return mDeviceContext->GfxUnitsToAppUnits(aGfxUnits);
+}
+
+gfxFloat nsPresContext::AppUnitsToGfxUnits(nscoord aAppUnits) const {
+  return mDeviceContext->AppUnitsToGfxUnits(aAppUnits);
+}
+
+nscoord nsPresContext::PhysicalMillimetersToAppUnits(float aMM) const {
+  float inches = aMM / MM_PER_INCH_FLOAT;
+  return NSToCoordFloorClamped(
+      inches * float(DeviceContext()->AppUnitsPerPhysicalInch()));
+}
+
+bool nsPresContext::IsDeviceSizePageSize() {
+  nsIDocShell* docShell = GetDocShell();
+  return docShell && docShell->GetDeviceSizeIsPageSize();
+}
+
+uint64_t nsPresContext::GetRestyleGeneration() const {
+  if (!mRestyleManager) {
+    return 0;
+  }
+  return mRestyleManager->GetRestyleGeneration();
+}
+
+uint64_t nsPresContext::GetUndisplayedRestyleGeneration() const {
+  if (!mRestyleManager) {
+    return 0;
+  }
+  return mRestyleManager->GetUndisplayedRestyleGeneration();
+}
+
+nsBidi& nsPresContext::GetBidiEngine() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!mBidiEngine) {
+    mBidiEngine.reset(new nsBidi());
+  }
+  return *mBidiEngine;
+}
+
+void nsPresContext::FlushFontFeatureValues() {
+  if (!mPresShell) {
+    return;  // we've been torn down
+  }
+
+  if (mFontFeatureValuesDirty) {
+    ServoStyleSet* styleSet = mPresShell->StyleSet();
+    mFontFeatureValuesLookup = styleSet->BuildFontFeatureValueSet();
+    mFontFeatureValuesDirty = false;
+  }
+}
+
+void nsPresContext::SetVisibleArea(const nsRect& r) {
+  if (!r.IsEqualEdges(mVisibleArea)) {
+    mVisibleArea = r;
+    mSizeForViewportUnits = mVisibleArea.Size();
+    if (IsRootContentDocumentCrossProcess()) {
+      AdjustSizeForViewportUnits();
+    }
+    // Visible area does not affect media queries when paginated.
+    if (!IsPaginated()) {
+      MediaFeatureValuesChanged(
+          {mozilla::MediaFeatureChangeReason::ViewportChange},
+          MediaFeatureChangePropagation::JustThisDocument);
+    }
+  }
+}
+
+void nsPresContext::SetDynamicToolbarMaxHeight(ScreenIntCoord aHeight) {
+  MOZ_ASSERT(IsRootContentDocumentCrossProcess());
+
+  if (mDynamicToolbarMaxHeight == aHeight) {
+    return;
+  }
+  mDynamicToolbarMaxHeight = aHeight;
+  mDynamicToolbarHeight = aHeight;
+
+  AdjustSizeForViewportUnits();
+
+  if (RefPtr<mozilla::PresShell> presShell = mPresShell) {
+    // Changing the max height of the dynamic toolbar changes the ICB size, we
+    // need to kick a reflow with the current window dimensions since the max
+    // height change doesn't change the window dimensions but
+    // PresShell::ResizeReflow ends up subtracting the new dynamic toolbar
+    // height from the window dimensions and kick a reflow with the proper ICB
+    // size.
+    nscoord currentWidth, currentHeight;
+    presShell->GetViewManager()->GetWindowDimensions(&currentWidth,
+                                                     &currentHeight);
+    presShell->ResizeReflow(currentWidth, currentHeight,
+                            ResizeReflowOptions::NoOption);
+  }
+}
+
+void nsPresContext::AdjustSizeForViewportUnits() {
+  MOZ_ASSERT(IsRootContentDocumentCrossProcess());
+  if (mVisibleArea.height == NS_UNCONSTRAINEDSIZE) {
+    // Ignore `NS_UNCONSTRAINEDSIZE` since it's a temporary state during a
+    // reflow. We will end up calling this function again with a proper size in
+    // the same reflow.
+    return;
+  }
+
+  if (MOZ_UNLIKELY(mVisibleArea.height +
+                       NSIntPixelsToAppUnits(mDynamicToolbarMaxHeight,
+                                             mCurAppUnitsPerDevPixel) >
+                   nscoord_MAX)) {
+    MOZ_ASSERT_UNREACHABLE("The dynamic toolbar max height is probably wrong");
+    return;
+  }
+
+  mSizeForViewportUnits.height =
+      mVisibleArea.height +
+      NSIntPixelsToAppUnits(mDynamicToolbarMaxHeight, mCurAppUnitsPerDevPixel);
+}
+
+void nsPresContext::UpdateDynamicToolbarOffset(ScreenIntCoord aOffset) {
+  MOZ_ASSERT(IsRootContentDocumentCrossProcess());
+  if (!mPresShell) {
+    return;
+  }
+
+  if (!HasDynamicToolbar()) {
+    return;
+  }
+
+  MOZ_ASSERT(-mDynamicToolbarMaxHeight <= aOffset && aOffset <= 0);
+  if (mDynamicToolbarHeight == mDynamicToolbarMaxHeight + aOffset) {
+    return;
+  }
+
+  // Forcibly flush position:fixed elements in the case where the dynamic
+  // toolbar is going to be completely hidden or starts to be visible so that
+  // %-based style values will be recomputed with the visual viewport size which
+  // is including the area covered by the dynamic toolbar.
+  if (mDynamicToolbarHeight == 0 || aOffset == -mDynamicToolbarMaxHeight) {
+    mPresShell->MarkFixedFramesForReflow(IntrinsicDirty::Resize);
+    mPresShell->AddResizeEventFlushObserverIfNeeded();
+  }
+
+  mDynamicToolbarHeight = mDynamicToolbarMaxHeight + aOffset;
+
+  if (RefPtr<MobileViewportManager> mvm =
+          mPresShell->GetMobileViewportManager()) {
+    mvm->UpdateVisualViewportSizeByDynamicToolbar(-aOffset);
+  }
+}
+
+DynamicToolbarState nsPresContext::GetDynamicToolbarState() const {
+  if (!IsRootContentDocumentCrossProcess() || !HasDynamicToolbar()) {
+    return DynamicToolbarState::None;
+  }
+
+  if (mDynamicToolbarMaxHeight == mDynamicToolbarHeight) {
+    return DynamicToolbarState::Expanded;
+  } else if (mDynamicToolbarHeight == 0) {
+    return DynamicToolbarState::Collapsed;
+  }
+  return DynamicToolbarState::InTransition;
+}
+
+void nsPresContext::SetSafeAreaInsets(const ScreenIntMargin& aSafeAreaInsets) {
+  if (mSafeAreaInsets == aSafeAreaInsets) {
+    return;
+  }
+  mSafeAreaInsets = aSafeAreaInsets;
+
+  PostRebuildAllStyleDataEvent(nsChangeHint(0),
+                               RestyleHint::RecascadeSubtree());
+}
+
+#ifdef DEBUG
+
+void nsPresContext::ValidatePresShellAndDocumentReleation() const {
+  NS_ASSERTION(!mPresShell || !mPresShell->GetDocument() ||
+                   mPresShell->GetDocument() == mDocument,
+               "nsPresContext doesn't have the same document as nsPresShell!");
+}
+
+#endif  // #ifdef DEBUG
+
+nsRootPresContext::nsRootPresContext(dom::Document* aDocument,
+                                     nsPresContextType aType)
+    : nsPresContext(aDocument, aType) {}
+
+nsRootPresContext::~nsRootPresContext() {
+  NS_ASSERTION(mRegisteredPlugins.Count() == 0,
+               "All plugins should have been unregistered");
+  CancelApplyPluginGeometryTimer();
+}
+
+void nsRootPresContext::RegisterPluginForGeometryUpdates(nsIContent* aPlugin) {
+  mRegisteredPlugins.PutEntry(aPlugin);
+}
+
+void nsRootPresContext::UnregisterPluginForGeometryUpdates(
+    nsIContent* aPlugin) {
+  mRegisteredPlugins.RemoveEntry(aPlugin);
+}
+
+void nsRootPresContext::ComputePluginGeometryUpdates(
+    nsIFrame* aFrame, nsDisplayListBuilder* aBuilder, nsDisplayList* aList) {
+  if (mRegisteredPlugins.Count() == 0) {
+    return;
+  }
+
+  // Initially make the next state for each plugin descendant of aFrame be
+  // "hidden". Plugins that are visible will have their next state set to
+  // unhidden by nsDisplayPlugin::ComputeVisibility.
+  for (auto iter = mRegisteredPlugins.Iter(); !iter.Done(); iter.Next()) {
+    auto f =
+        static_cast<nsPluginFrame*>(iter.Get()->GetKey()->GetPrimaryFrame());
+    if (!f) {
+      NS_WARNING("Null frame in ComputePluginGeometryUpdates");
+      continue;
+    }
+    if (!nsLayoutUtils::IsAncestorFrameCrossDoc(aFrame, f)) {
+      // f is not managed by this frame so we should ignore it.
+      continue;
+    }
+    f->SetEmptyWidgetConfiguration();
+  }
+
+  if (aBuilder) {
+    MOZ_ASSERT(aList);
+    nsIFrame* rootFrame = mPresShell->GetRootFrame();
+
+    if (rootFrame && aBuilder->ContainsPluginItem()) {
+      aBuilder->SetForPluginGeometry(true);
+      // Merging and flattening has already been done and we should not do it
+      // again. nsDisplayScroll(Info)Layer doesn't support trying to flatten
+      // again.
+      aBuilder->SetAllowMergingAndFlattening(false);
+      nsRegion region = rootFrame->InkOverflowRectRelativeToSelf();
+      // nsDisplayPlugin::ComputeVisibility will automatically set a non-hidden
+      // widget configuration for the plugin, if it's visible.
+      aList->ComputeVisibilityForRoot(aBuilder, &region);
+      aBuilder->SetForPluginGeometry(false);
+    }
+  }
+
+#ifdef XP_MACOSX
+  // We control painting of Mac plugins, so just apply geometry updates now.
+  // This is not happening during a paint event.
+  ApplyPluginGeometryUpdates();
+#else
+  if (XRE_IsParentProcess()) {
+    InitApplyPluginGeometryTimer();
+  }
+#endif
+}
+
+static void ApplyPluginGeometryUpdatesCallback(nsITimer* aTimer,
+                                               void* aClosure) {
+  static_cast<nsRootPresContext*>(aClosure)->ApplyPluginGeometryUpdates();
+}
+
+void nsRootPresContext::InitApplyPluginGeometryTimer() {
+  if (mApplyPluginGeometryTimer) {
+    return;
+  }
+
+  // We'll apply the plugin geometry updates during the next compositing paint
+  // in this presContext (either from PresShell::WillPaintWindow() or from
+  // PresShell::DidPaintWindow(), depending on the platform).  But paints might
+  // get optimized away if the old plugin geometry covers the invalid region,
+  // so set a backup timer to do this too.  We want to make sure this
+  // won't fire before our normal paint notifications, if those would
+  // update the geometry, so set it for double the refresh driver interval.
+  mApplyPluginGeometryTimer = CreateTimer(
+      ApplyPluginGeometryUpdatesCallback, "ApplyPluginGeometryUpdatesCallback",
+      nsRefreshDriver::DefaultInterval() * 2);
+}
+
+void nsRootPresContext::CancelApplyPluginGeometryTimer() {
+  if (mApplyPluginGeometryTimer) {
+    mApplyPluginGeometryTimer->Cancel();
+    mApplyPluginGeometryTimer = nullptr;
+  }
+}
+
+#ifndef XP_MACOSX
+
+static bool HasOverlap(const LayoutDeviceIntPoint& aOffset1,
+                       const nsTArray<LayoutDeviceIntRect>& aClipRects1,
+                       const LayoutDeviceIntPoint& aOffset2,
+                       const nsTArray<LayoutDeviceIntRect>& aClipRects2) {
+  LayoutDeviceIntPoint offsetDelta = aOffset1 - aOffset2;
+  for (uint32_t i = 0; i < aClipRects1.Length(); ++i) {
+    for (uint32_t j = 0; j < aClipRects2.Length(); ++j) {
+      if ((aClipRects1[i] + offsetDelta).Intersects(aClipRects2[j])) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+/**
+ * Given a list of plugin windows to move to new locations, sort the list
+ * so that for each window move, the window moves to a location that
+ * does not intersect other windows. This minimizes flicker and repainting.
+ * It's not always possible to do this perfectly, since in general
+ * we might have cycles. But we do our best.
+ * We need to take into account that windows are clipped to particular
+ * regions and the clip regions change as the windows are moved.
+ */
+static void SortConfigurations(
+    nsTArray<nsIWidget::Configuration>* aConfigurations) {
+  if (aConfigurations->Length() > 10) {
+    // Give up, we don't want to get bogged down here
+    return;
+  }
+
+  nsTArray<nsIWidget::Configuration> pluginsToMove =
+      std::move(*aConfigurations);
+
+  // Our algorithm is quite naive. At each step we try to identify
+  // a window that can be moved to its new location that won't overlap
+  // any other windows at the new location. If there is no such
+  // window, we just move the last window in the list anyway.
+  while (!pluginsToMove.IsEmpty()) {
+    // Find a window whose destination does not overlap any other window
+    uint32_t i;
+    for (i = 0; i + 1 < pluginsToMove.Length(); ++i) {
+      nsIWidget::Configuration* config = &pluginsToMove[i];
+      bool foundOverlap = false;
+      for (uint32_t j = 0; j < pluginsToMove.Length(); ++j) {
+        if (i == j) continue;
+        LayoutDeviceIntRect bounds = pluginsToMove[j].mChild->GetBounds();
+        AutoTArray<LayoutDeviceIntRect, 1> clipRects;
+        pluginsToMove[j].mChild->GetWindowClipRegion(&clipRects);
+        if (HasOverlap(bounds.TopLeft(), clipRects, config->mBounds.TopLeft(),
+                       config->mClipRegion)) {
+          foundOverlap = true;
+          break;
+        }
+      }
+      if (!foundOverlap) break;
+    }
+    // Note that we always move the last plugin in pluginsToMove, if we
+    // can't find any other plugin to move
+    aConfigurations->AppendElement(pluginsToMove[i]);
+    pluginsToMove.RemoveElementAt(i);
+  }
+}
+
+static void PluginGetGeometryUpdate(
+    nsTHashtable<nsRefPtrHashKey<nsIContent>>& aPlugins,
+    nsTArray<nsIWidget::Configuration>* aConfigurations) {
+  for (auto iter = aPlugins.Iter(); !iter.Done(); iter.Next()) {
+    auto f =
+        static_cast<nsPluginFrame*>(iter.Get()->GetKey()->GetPrimaryFrame());
+    if (!f) {
+      NS_WARNING("Null frame in PluginGeometryUpdate");
+      continue;
+    }
+    f->GetWidgetConfiguration(aConfigurations);
+  }
+}
+
+#endif  // #ifndef XP_MACOSX
+
+static void PluginDidSetGeometry(
+    nsTHashtable<nsRefPtrHashKey<nsIContent>>& aPlugins) {
+  for (auto iter = aPlugins.Iter(); !iter.Done(); iter.Next()) {
+    auto f =
+        static_cast<nsPluginFrame*>(iter.Get()->GetKey()->GetPrimaryFrame());
+    if (!f) {
+      NS_WARNING("Null frame in PluginDidSetGeometry");
+      continue;
+    }
+    f->DidSetWidgetGeometry();
+  }
+}
+
+void nsRootPresContext::ApplyPluginGeometryUpdates() {
+#ifndef XP_MACOSX
+  CancelApplyPluginGeometryTimer();
+
+  nsTArray<nsIWidget::Configuration> configurations;
+  PluginGetGeometryUpdate(mRegisteredPlugins, &configurations);
+  // Walk mRegisteredPlugins and ask each plugin for its configuration
+  if (!configurations.IsEmpty()) {
+    nsIWidget* widget = configurations[0].mChild->GetParent();
+    NS_ASSERTION(widget, "Plugins must have a parent window");
+    SortConfigurations(&configurations);
+    widget->ConfigureChildren(configurations);
+  }
+#endif  // #ifndef XP_MACOSX
+
+  PluginDidSetGeometry(mRegisteredPlugins);
+}
+
+void nsRootPresContext::CollectPluginGeometryUpdates(
+    LayerManager* aLayerManager) {
+#ifndef XP_MACOSX
+  // Collect and pass plugin widget configurations down to the compositor
+  // for transmission to the chrome process.
+  NS_ASSERTION(aLayerManager, "layer manager is invalid!");
+  mozilla::layers::ClientLayerManager* clm =
+      aLayerManager->AsClientLayerManager();
+
+  nsTArray<nsIWidget::Configuration> configurations;
+  // If there aren't any plugins to configure, clear the plugin data cache
+  // in the layer system.
+  if (!mRegisteredPlugins.Count() && clm) {
+    clm->StorePluginWidgetConfigurations(configurations);
+    return;
+  }
+  PluginGetGeometryUpdate(mRegisteredPlugins, &configurations);
+  if (configurations.IsEmpty()) {
+    PluginDidSetGeometry(mRegisteredPlugins);
+    return;
+  }
+  SortConfigurations(&configurations);
+  if (clm) {
+    clm->StorePluginWidgetConfigurations(configurations);
+  }
+  PluginDidSetGeometry(mRegisteredPlugins);
+#endif  // #ifndef XP_MACOSX
+}
+
+void nsRootPresContext::AddWillPaintObserver(nsIRunnable* aRunnable) {
+  if (!mWillPaintFallbackEvent.IsPending()) {
+    mWillPaintFallbackEvent = new RunWillPaintObservers(this);
+    Document()->Dispatch(TaskCategory::Other,
+                         do_AddRef(mWillPaintFallbackEvent));
+  }
+  mWillPaintObservers.AppendElement(aRunnable);
+}
+
+/**
+ * Run all runnables that need to get called before the next paint.
+ */
+void nsRootPresContext::FlushWillPaintObservers() {
+  mWillPaintFallbackEvent = nullptr;
+  nsTArray<nsCOMPtr<nsIRunnable>> observers = std::move(mWillPaintObservers);
+  for (uint32_t i = 0; i < observers.Length(); ++i) {
+    observers[i]->Run();
+  }
+}
+
+size_t nsRootPresContext::SizeOfExcludingThis(
+    MallocSizeOf aMallocSizeOf) const {
+  return nsPresContext::SizeOfExcludingThis(aMallocSizeOf);
+
+  // Measurement of the following members may be added later if DMD finds it is
+  // worthwhile:
+  // - mRegisteredPlugins
+  // - mWillPaintObservers
+  // - mWillPaintFallbackEvent
+}
-- 
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