From 425dc7f02b6cc488e32c8ec762c100d3313d7ea7 Mon Sep 17 00:00:00 2001
From: FranklinDM <mrmineshafter17@gmail.com>
Date: Mar 25 2024 17:25:53 +0000
Subject: Issue #2112 - Part 9: Remove handling for multiple style backends


---

diff --git a/dom/animation/KeyframeUtils.cpp b/dom/animation/KeyframeUtils.cpp
index a89e954..1285611 100644
--- a/dom/animation/KeyframeUtils.cpp
+++ b/dom/animation/KeyframeUtils.cpp
@@ -318,7 +318,7 @@ public:
 // ------------------------------------------------------------------
 
 inline bool
-IsInvalidValuePair(const PropertyValuePair& aPair, StyleBackendType aBackend)
+IsInvalidValuePair(const PropertyValuePair& aPair)
 {
   // There are three types of values we store as token streams:
   //
@@ -595,8 +595,6 @@ KeyframeUtils::GetComputedKeyframeValues(const nsTArray<Keyframe>& aKeyframes,
   MOZ_ASSERT(aStyleContext);
   MOZ_ASSERT(aElement);
 
-  StyleBackendType styleBackend = aElement->OwnerDoc()->GetStyleBackendType();
-
   const size_t len = aKeyframes.Length();
   nsTArray<ComputedKeyframeValues> result(len);
 
@@ -605,7 +603,7 @@ KeyframeUtils::GetComputedKeyframeValues(const nsTArray<Keyframe>& aKeyframes,
     ComputedKeyframeValues* computedValues = result.AppendElement();
     for (const PropertyValuePair& pair :
            PropertyPriorityIterator(frame.mPropertyValues)) {
-      if (IsInvalidValuePair(pair, styleBackend)) {
+      if (IsInvalidValuePair(pair)) {
         continue;
       }
 
@@ -1363,8 +1361,6 @@ HasImplicitKeyframeValues(const nsTArray<Keyframe>& aKeyframes,
     }
   };
 
-  StyleBackendType styleBackend = aDocument->GetStyleBackendType();
-
   for (size_t i = 0, len = aKeyframes.Length(); i < len; i++) {
     const Keyframe& frame = aKeyframes[i];
 
@@ -1380,7 +1376,7 @@ HasImplicitKeyframeValues(const nsTArray<Keyframe>& aKeyframes,
                          : computedOffset;
 
     for (const PropertyValuePair& pair : frame.mPropertyValues) {
-      if (IsInvalidValuePair(pair, styleBackend)) {
+      if (IsInvalidValuePair(pair)) {
         continue;
       }
 
diff --git a/dom/base/nsDocument.cpp b/dom/base/nsDocument.cpp
index 844f298..a4c2b48 100644
--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -2108,21 +2108,16 @@ nsDocument::ResetStylesheetsToURI(nsIURI* aURI)
   mozAutoDocUpdate upd(this, UPDATE_STYLE, true);
   if (mStyleSetFilled) {
     // Skip removing style sheets from the style set if we know we haven't
-    // filled the style set.  (This allows us to avoid calling
-    // GetStyleBackendType() too early.)
+    // filled the style set.
     RemoveDocStyleSheetsFromStyleSets();
     RemoveStyleSheetsFromStyleSets(mOnDemandBuiltInUASheets, SheetType::Agent);
     RemoveStyleSheetsFromStyleSets(mAdditionalSheets[eAgentSheet], SheetType::Agent);
     RemoveStyleSheetsFromStyleSets(mAdditionalSheets[eUserSheet], SheetType::User);
     RemoveStyleSheetsFromStyleSets(mAdditionalSheets[eAuthorSheet], SheetType::Doc);
 
-    if (GetStyleBackendType() == StyleBackendType::Gecko) {
-      nsStyleSheetService *sheetService = nsStyleSheetService::GetInstance();
-      if (sheetService) {
-        RemoveStyleSheetsFromStyleSets(*sheetService->AuthorStyleSheets(), SheetType::Doc);
-      }
-    } else {
-      NS_ERROR("stylo: nsStyleSheetService doesn't handle ServoStyleSheets yet");
+    nsStyleSheetService *sheetService = nsStyleSheetService::GetInstance();
+    if (sheetService) {
+      RemoveStyleSheetsFromStyleSets(*sheetService->AuthorStyleSheets(), SheetType::Doc);
     }
 
     mStyleSetFilled = false;
@@ -12211,16 +12206,6 @@ nsIDocument::ReportHasScrollLinkedEffect()
                                   "ScrollLinkedEffectFound2");
 }
 
-void
-nsIDocument::UpdateStyleBackendType()
-{
-  MOZ_ASSERT(mStyleBackendType == StyleBackendType(0),
-             "no need to call UpdateStyleBackendType now");
-
-  // Assume Gecko by default.
-  mStyleBackendType = StyleBackendType::Gecko;
-}
-
 Selection*
 nsIDocument::GetSelection(ErrorResult& aRv)
 {
diff --git a/dom/base/nsIDocument.h b/dom/base/nsIDocument.h
index e6def66..5608973 100644
--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -34,7 +34,6 @@
 #include "mozilla/CORSMode.h"
 #include "mozilla/dom/DocumentOrShadowRoot.h"
 #include "mozilla/LinkedList.h"
-#include "mozilla/StyleBackendType.h"
 #include "mozilla/StyleSheet.h"
 #include "mozilla/TimeStamp.h"
 #include <bitset>                        // for member
@@ -1148,16 +1147,6 @@ public:
     return mCSSLoader;
   }
 
-  mozilla::StyleBackendType GetStyleBackendType() const {
-    if (mStyleBackendType == mozilla::StyleBackendType(0)) {
-      const_cast<nsIDocument*>(this)->UpdateStyleBackendType();
-    }
-    MOZ_ASSERT(mStyleBackendType != mozilla::StyleBackendType(0));
-    return mStyleBackendType;
-  }
-
-  void UpdateStyleBackendType();
-
   /**
    * Get this document's StyleImageLoader.  This is guaranteed to not return null.
    */
@@ -2975,10 +2964,6 @@ protected:
   uint32_t mDummy;
 #endif
 
-  // Whether this document has (or will have, once we have a pres shell) a
-  // Gecko- or Servo-backed style system.
-  mozilla::StyleBackendType mStyleBackendType;
-
   // True if BIDI is enabled.
   bool mBidiEnabled : 1;
   // True if a MathML element has ever been owned by this document.
diff --git a/layout/base/RestyleManagerHandle.h b/layout/base/RestyleManagerHandle.h
index 2f6467a..9087347 100644
--- a/layout/base/RestyleManagerHandle.h
+++ b/layout/base/RestyleManagerHandle.h
@@ -10,7 +10,6 @@
 #include "mozilla/EventStates.h"
 #include "mozilla/HandleRefPtr.h"
 #include "mozilla/RefCountType.h"
-#include "mozilla/StyleBackendType.h"
 #include "nsChangeHint.h"
 
 namespace mozilla {
@@ -48,11 +47,6 @@ public:
   public:
     friend class ::mozilla::RestyleManagerHandle;
 
-    StyleBackendType BackendType() const
-    {
-      return StyleBackendType::Gecko;
-    }
-
     RestyleManager* AsGecko()
     {
       return reinterpret_cast<RestyleManager*>(mValue);
diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index 62b3d89..4f78acb 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -9115,14 +9115,6 @@ nsLayoutUtils::GetCumulativeApzCallbackTransform(nsIFrame* aFrame)
   return delta;
 }
 
-/* static */ bool
-nsLayoutUtils::SupportsServoStyleBackend(nsIDocument* aDocument)
-{
-  return StyloEnabled() &&
-         aDocument->IsHTMLOrXHTML() &&
-         static_cast<nsDocument*>(aDocument)->IsContentDocument();
-}
-
 static
 bool
 LineHasNonEmptyContentWorker(nsIFrame* aFrame)
diff --git a/layout/base/nsLayoutUtils.h b/layout/base/nsLayoutUtils.h
index 29cd655..7d2b6f6 100644
--- a/layout/base/nsLayoutUtils.h
+++ b/layout/base/nsLayoutUtils.h
@@ -2379,13 +2379,6 @@ public:
     return sTextCombineUprightDigitsEnabled;
   }
 
-  // Stylo (the Servo backend for Gecko's style system) is generally enabled
-  // or disabled at compile-time. However, we provide the additional capability
-  // to disable it dynamically in stylo-enabled builds via a pref.
-  static bool StyloEnabled() {
-    return false;
-  }
-
   static uint32_t IdlePeriodDeadlineLimit() {
     return sIdlePeriodDeadlineLimit;
   }
@@ -2814,14 +2807,6 @@ public:
   static CSSPoint GetCumulativeApzCallbackTransform(nsIFrame* aFrame);
 
   /*
-   * Returns whether the given document supports being rendered with a
-   * Servo-backed style system.  This checks whether Stylo is enabled
-   * globally, that the document is an HTML document, and that it is
-   * being presented in a content docshell.
-   */
-  static bool SupportsServoStyleBackend(nsIDocument* aDocument);
-
-  /*
    * Checks whether a node is an invisible break.
    * If not, returns the first frame on the next line if such a next line exists.
    *
diff --git a/layout/base/nsPresContext.cpp b/layout/base/nsPresContext.cpp
index ef62a32..92fab43 100644
--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -891,7 +891,7 @@ nsPresContext::Init(nsDeviceContext* aDeviceContext)
 // Note: We don't hold a reference on the shell; it has a reference to
 // us
 void
-nsPresContext::AttachShell(nsIPresShell* aShell, StyleBackendType aBackendType)
+nsPresContext::AttachShell(nsIPresShell* aShell)
 {
   MOZ_ASSERT(!mShell);
   mShell = aShell;
diff --git a/layout/base/nsPresContext.h b/layout/base/nsPresContext.h
index 05edfc0..062ebff 100644
--- a/layout/base/nsPresContext.h
+++ b/layout/base/nsPresContext.h
@@ -42,7 +42,6 @@
 #include "mozilla/RestyleManagerHandle.h"
 #include "prenv.h"
 #include "mozilla/StaticPresData.h"
-#include "mozilla/StyleBackendType.h"
 
 class nsAString;
 class nsIPrintSettings;
@@ -169,7 +168,7 @@ public:
    * Set and detach presentation shell that this context is bound to.
    * A presentation context may only be bound to a single shell.
    */
-  void AttachShell(nsIPresShell* aShell, mozilla::StyleBackendType aBackendType);
+  void AttachShell(nsIPresShell* aShell);
   void DetachShell();
 
 
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index 122e3ae..cd40bd2 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -34,7 +34,6 @@
 #include "mozilla/TouchEvents.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/Unused.h"
-#include "mozilla/StyleBackendType.h"
 #include <algorithm>
 
 #ifdef XP_WIN
@@ -887,8 +886,7 @@ PresShell::Init(nsIDocument* aDocument,
 
   // Bind the context to the presentation shell.
   mPresContext = aPresContext;
-  StyleBackendType backend = StyleBackendType::Gecko;
-  aPresContext->AttachShell(this, backend);
+  aPresContext->AttachShell(this);
 
   // Now we can initialize the style set. Make sure to set the member before
   // calling Init, since various subroutines need to find the style set off
diff --git a/layout/style/CSS.cpp b/layout/style/CSS.cpp
index 1078945..49ea6ee 100644
--- a/layout/style/CSS.cpp
+++ b/layout/style/CSS.cpp
@@ -24,7 +24,6 @@ struct SupportsParsingInfo
   nsIURI* mDocURI;
   nsIURI* mBaseURI;
   nsIPrincipal* mPrincipal;
-  StyleBackendType mStyleBackendType;
 };
 
 static nsresult
@@ -44,7 +43,6 @@ GetParsingInfo(const GlobalObject& aGlobal,
   aInfo.mDocURI = nsCOMPtr<nsIURI>(doc->GetDocumentURI()).get();
   aInfo.mBaseURI = nsCOMPtr<nsIURI>(doc->GetBaseURI()).get();
   aInfo.mPrincipal = win->GetPrincipal();
-  aInfo.mStyleBackendType = doc->GetStyleBackendType();
   return NS_OK;
 }
 
diff --git a/layout/style/CSSStyleSheet.cpp b/layout/style/CSSStyleSheet.cpp
index 7c9e433..1cb99ec 100644
--- a/layout/style/CSSStyleSheet.cpp
+++ b/layout/style/CSSStyleSheet.cpp
@@ -1083,7 +1083,7 @@ CSSStyleSheetInner::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
 
 CSSStyleSheet::CSSStyleSheet(css::SheetParsingMode aParsingMode,
                              CORSMode aCORSMode, ReferrerPolicy aReferrerPolicy)
-  : StyleSheet(StyleBackendType::Gecko, aParsingMode),
+  : StyleSheet(aParsingMode),
     mParent(nullptr),
     mOwnerRule(nullptr),
     mDirty(false),
@@ -1099,7 +1099,7 @@ CSSStyleSheet::CSSStyleSheet(css::SheetParsingMode aParsingMode,
                              CORSMode aCORSMode,
                              ReferrerPolicy aReferrerPolicy,
                              const SRIMetadata& aIntegrity)
-  : StyleSheet(StyleBackendType::Gecko, aParsingMode),
+  : StyleSheet(aParsingMode),
     mParent(nullptr),
     mOwnerRule(nullptr),
     mDirty(false),
diff --git a/layout/style/Declaration.h b/layout/style/Declaration.h
index a18c38b..e3ab955 100644
--- a/layout/style/Declaration.h
+++ b/layout/style/Declaration.h
@@ -92,7 +92,7 @@ public:
    * |mData|) and cannot be used until its |CompressFrom| method or
    * |InitializeEmpty| method is called.
    */
-  Declaration() : DeclarationBlock(StyleBackendType::Gecko) {}
+  Declaration() : DeclarationBlock() {}
 
   Declaration(const Declaration& aCopy);
 
diff --git a/layout/style/DeclarationBlock.h b/layout/style/DeclarationBlock.h
index 6a10c59..9a0c9db 100644
--- a/layout/style/DeclarationBlock.h
+++ b/layout/style/DeclarationBlock.h
@@ -12,7 +12,6 @@
 #define mozilla_DeclarationBlock_h
 
 #include "mozilla/ServoUtils.h"
-#include "mozilla/StyleBackendType.h"
 
 #include "nsCSSPropertyID.h"
 
@@ -30,11 +29,11 @@ class Rule;
 class DeclarationBlock
 {
 protected:
-  explicit DeclarationBlock(StyleBackendType aType)
-    : mImmutable(false), mType(aType) { mContainer.mRaw = 0; }
+  explicit DeclarationBlock()
+    : mImmutable(false) { mContainer.mRaw = 0; }
 
   DeclarationBlock(const DeclarationBlock& aCopy)
-    : DeclarationBlock(aCopy.mType) {}
+    : DeclarationBlock() {}
 
 public:
   MOZ_DECL_STYLO_METHODS(css::Declaration)
@@ -136,8 +135,6 @@ private:
   // set when declaration put in the rule tree;
   // also by ToString (hence the 'mutable').
   mutable bool mImmutable;
-
-  const StyleBackendType mType;
 };
 
 } // namespace mozilla
diff --git a/layout/style/ServoDeclarationBlock.h b/layout/style/ServoDeclarationBlock.h
index 2cf7b16..ccc05d6 100644
--- a/layout/style/ServoDeclarationBlock.h
+++ b/layout/style/ServoDeclarationBlock.h
@@ -59,7 +59,7 @@ public:
 protected:
   explicit ServoDeclarationBlock(
     already_AddRefed<RawServoDeclarationBlock> aRaw)
-    : DeclarationBlock(StyleBackendType::Servo), mRaw(aRaw) {}
+    : DeclarationBlock(), mRaw(aRaw) {}
 
 private:
   ~ServoDeclarationBlock() {}
diff --git a/layout/style/ServoStyleSheet.cpp b/layout/style/ServoStyleSheet.cpp
index dc9fc34..daec2f8 100644
--- a/layout/style/ServoStyleSheet.cpp
+++ b/layout/style/ServoStyleSheet.cpp
@@ -5,7 +5,6 @@
 
 #include "ServoBindings.h"
 #include "mozilla/ServoStyleSheet.h"
-#include "mozilla/StyleBackendType.h"
 #include "CSSRuleList.h"
 
 using namespace mozilla::dom;
@@ -16,7 +15,7 @@ ServoStyleSheet::ServoStyleSheet(css::SheetParsingMode aParsingMode,
                                  CORSMode aCORSMode,
                                  net::ReferrerPolicy aReferrerPolicy,
                                  const dom::SRIMetadata& aIntegrity)
-  : StyleSheet(StyleBackendType::Servo, aParsingMode)
+  : StyleSheet(aParsingMode)
   , mSheetInfo(aCORSMode, aReferrerPolicy, aIntegrity)
 {
 }
diff --git a/layout/style/StyleBackendType.h b/layout/style/StyleBackendType.h
deleted file mode 100644
index 99d5c15..0000000
--- a/layout/style/StyleBackendType.h
+++ /dev/null
@@ -1,22 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* 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/. */
-
-#ifndef mozilla_StyleBackendType_h
-#define mozilla_StyleBackendType_h
-
-namespace mozilla {
-
-/**
- * Enumeration that represents one of the two supported style system backends.
- */
-enum class StyleBackendType : uint8_t
-{
-  Gecko = 1,
-  Servo
-};
-
-} // namespace mozilla
-
-#endif // mozilla_StyleBackendType_h
diff --git a/layout/style/StyleSetHandle.h b/layout/style/StyleSetHandle.h
index 1095824..6d17c71 100644
--- a/layout/style/StyleSetHandle.h
+++ b/layout/style/StyleSetHandle.h
@@ -9,7 +9,6 @@
 #include "mozilla/EventStates.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/SheetType.h"
-#include "mozilla/StyleBackendType.h"
 #include "mozilla/StyleSheet.h"
 #include "nsChangeHint.h"
 #include "nsCSSPseudoElements.h"
@@ -46,11 +45,6 @@ public:
   public:
     friend class ::mozilla::StyleSetHandle;
 
-    StyleBackendType BackendType() const
-    {
-      return StyleBackendType::Gecko;
-    }
-
     nsStyleSet* AsGecko()
     {
       return reinterpret_cast<nsStyleSet*>(mValue);
diff --git a/layout/style/StyleSheet.cpp b/layout/style/StyleSheet.cpp
index 7109f73..9af37c4 100644
--- a/layout/style/StyleSheet.cpp
+++ b/layout/style/StyleSheet.cpp
@@ -20,11 +20,10 @@ using namespace mozilla::dom;
 
 namespace mozilla {
 
-StyleSheet::StyleSheet(StyleBackendType aType, css::SheetParsingMode aParsingMode)
+StyleSheet::StyleSheet(css::SheetParsingMode aParsingMode)
   : mDocument(nullptr)
   , mOwningNode(nullptr)
   , mParsingMode(aParsingMode)
-  , mType(aType)
   , mDisabled(false)
   , mDocumentAssociationMode(NotOwnedByDocument)
 {
@@ -37,7 +36,6 @@ StyleSheet::StyleSheet(const StyleSheet& aCopy,
   , mDocument(aDocumentToUse)
   , mOwningNode(aOwningNodeToUse)
   , mParsingMode(aCopy.mParsingMode)
-  , mType(aCopy.mType)
   , mDisabled(aCopy.mDisabled)
     // We only use this constructor during cloning.  It's the cloner's
     // responsibility to notify us if we end up being owned by a document.
diff --git a/layout/style/StyleSheet.h b/layout/style/StyleSheet.h
index e40d8f6..94ff05c 100644
--- a/layout/style/StyleSheet.h
+++ b/layout/style/StyleSheet.h
@@ -9,7 +9,6 @@
 #include "mozilla/css/SheetParsingMode.h"
 #include "mozilla/dom/CSSStyleSheetBinding.h"
 #include "mozilla/net/ReferrerPolicy.h"
-#include "mozilla/StyleBackendType.h"
 #include "mozilla/CORSMode.h"
 #include "mozilla/ServoUtils.h"
 
@@ -39,7 +38,7 @@ class StyleSheet : public nsIDOMCSSStyleSheet
                  , public nsWrapperCache
 {
 protected:
-  StyleSheet(StyleBackendType aType, css::SheetParsingMode aParsingMode);
+  StyleSheet(css::SheetParsingMode aParsingMode);
   StyleSheet(const StyleSheet& aCopy,
              nsIDocument* aDocumentToUse,
              nsINode* aOwningNodeToUse);
@@ -218,7 +217,6 @@ protected:
   // and/or useful in user sheets.
   css::SheetParsingMode mParsingMode;
 
-  const StyleBackendType mType;
   bool                  mDisabled;
 
   // mDocumentAssociationMode determines whether mDocument directly owns us (in
diff --git a/layout/style/moz.build b/layout/style/moz.build
index 48072b0..1d221bd 100644
--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -97,7 +97,6 @@ EXPORTS.mozilla += [
     'ServoUtils.h',
     'SheetType.h',
     'StyleAnimationValue.h',
-    'StyleBackendType.h',
     'StyleComplexColor.h',
     'StyleContextSource.h',
     'StyleSetHandle.h',