Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 634 insertions, 0 deletions

diff --git a/dom/bindings/DOMJSClass.h b/dom/bindings/DOMJSClass.h
new file mode 100644
index 0000000000..12055fe6ba
--- /dev/null
+++ b/dom/bindings/DOMJSClass.h
@@ -0,0 +1,634 @@
+/* -*- 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/. */
+
+#ifndef mozilla_dom_DOMJSClass_h
+#define mozilla_dom_DOMJSClass_h
+
+#include "jsapi.h"
+#include "jsfriendapi.h"
+#include "js/Object.h"  // JS::GetClass, JS::GetReservedSlot
+#include "js/Wrapper.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/OriginTrials.h"
+#include "mozilla/Likely.h"
+
+#include "mozilla/dom/PrototypeList.h"  // auto-generated
+#include "mozilla/dom/WebIDLPrefs.h"    // auto-generated
+
+class nsCycleCollectionParticipant;
+class nsWrapperCache;
+struct JSFunctionSpec;
+struct JSPropertySpec;
+struct JSStructuredCloneReader;
+struct JSStructuredCloneWriter;
+class nsIGlobalObject;
+
+// All DOM globals must have a slot at DOM_PROTOTYPE_SLOT.
+#define DOM_PROTOTYPE_SLOT JSCLASS_GLOBAL_SLOT_COUNT
+
+// Keep this count up to date with any extra global slots added above.
+#define DOM_GLOBAL_SLOTS 1
+
+// We use these flag bits for the new bindings.
+#define JSCLASS_DOM_GLOBAL JSCLASS_USERBIT1
+#define JSCLASS_IS_DOMIFACEANDPROTOJSCLASS JSCLASS_USERBIT2
+
+namespace mozilla::dom {
+
+/**
+ * Returns true if code running in the given JSContext is allowed to access
+ * [SecureContext] API on the given JSObject.
+ *
+ * [SecureContext] API exposure is restricted to use by code in a Secure
+ * Contexts:
+ *
+ *   https://w3c.github.io/webappsec-secure-contexts/
+ *
+ * Since we want [SecureContext] exposure to depend on the privileges of the
+ * running code (rather than the privileges of an object's creator), this
+ * function checks to see whether the given JSContext's Realm is flagged
+ * as a Secure Context.  That allows us to make sure that system principal code
+ * (which is marked as a Secure Context) can access Secure Context API on an
+ * object in a different realm, regardless of whether the other realm is a
+ * Secure Context or not.
+ *
+ * Checking the JSContext's Realm doesn't work for expanded principal
+ * globals accessing a Secure Context web page though (e.g. those used by frame
+ * scripts).  To handle that we fall back to checking whether the JSObject came
+ * from a Secure Context.
+ *
+ * Note: We'd prefer this function to live in BindingUtils.h, but we need to
+ * call it in this header, and BindingUtils.h includes us (i.e. we'd have a
+ * circular dependency between headers if it lived there).
+ */
+inline bool IsSecureContextOrObjectIsFromSecureContext(JSContext* aCx,
+                                                       JSObject* aObj) {
+  MOZ_ASSERT(!js::IsWrapper(aObj));
+  return JS::GetIsSecureContext(js::GetContextRealm(aCx)) ||
+         JS::GetIsSecureContext(js::GetNonCCWObjectRealm(aObj));
+}
+
+typedef bool (*ResolveOwnProperty)(
+    JSContext* cx, JS::Handle<JSObject*> wrapper, JS::Handle<JSObject*> obj,
+    JS::Handle<jsid> id,
+    JS::MutableHandle<mozilla::Maybe<JS::PropertyDescriptor>> desc);
+
+typedef bool (*EnumerateOwnProperties)(JSContext* cx,
+                                       JS::Handle<JSObject*> wrapper,
+                                       JS::Handle<JSObject*> obj,
+                                       JS::MutableHandleVector<jsid> props);
+
+typedef bool (*DeleteNamedProperty)(JSContext* cx,
+                                    JS::Handle<JSObject*> wrapper,
+                                    JS::Handle<JSObject*> obj,
+                                    JS::Handle<jsid> id,
+                                    JS::ObjectOpResult& opresult);
+
+// Returns true if the given global is of a type whose bit is set in
+// aGlobalSet.
+bool IsGlobalInExposureSet(JSContext* aCx, JSObject* aGlobal,
+                           uint32_t aGlobalSet);
+
+struct ConstantSpec {
+  const char* name;
+  JS::Value value;
+};
+
+typedef bool (*PropertyEnabled)(JSContext* cx, JSObject* global);
+
+namespace GlobalNames {
+// The names of our possible globals.  These are the names of the actual
+// interfaces, not of the global names used to refer to them in IDL [Exposed]
+// annotations.
+static const uint32_t Window = 1u << 0;
+static const uint32_t DedicatedWorkerGlobalScope = 1u << 1;
+static const uint32_t SharedWorkerGlobalScope = 1u << 2;
+static const uint32_t ServiceWorkerGlobalScope = 1u << 3;
+static const uint32_t WorkerDebuggerGlobalScope = 1u << 4;
+static const uint32_t AudioWorkletGlobalScope = 1u << 5;
+static const uint32_t PaintWorkletGlobalScope = 1u << 6;
+static const uint32_t ShadowRealmGlobalScope = 1u << 7;
+
+static constexpr uint32_t kCount = 8;
+}  // namespace GlobalNames
+
+struct PrefableDisablers {
+  inline bool isEnabled(JSContext* cx, JS::Handle<JSObject*> obj) const {
+    if (nonExposedGlobals &&
+        IsGlobalInExposureSet(cx, JS::GetNonCCWObjectGlobal(obj),
+                              nonExposedGlobals)) {
+      return false;
+    }
+    if (prefIndex != WebIDLPrefIndex::NoPref &&
+        !sWebIDLPrefs[uint16_t(prefIndex)]()) {
+      return false;
+    }
+    if (secureContext && !IsSecureContextOrObjectIsFromSecureContext(cx, obj)) {
+      return false;
+    }
+    if (trial != OriginTrial(0) &&
+        !OriginTrials::IsEnabled(cx, JS::GetNonCCWObjectGlobal(obj), trial)) {
+      // TODO(emilio): Perhaps reconsider the interaction between [Trial=""] and
+      // [Pref=""].
+      //
+      // In particular, it might be desirable to only check the trial if there
+      // is no pref or the pref is disabled.
+      return false;
+    }
+    if (enabledFunc && !enabledFunc(cx, JS::GetNonCCWObjectGlobal(obj))) {
+      return false;
+    }
+    return true;
+  }
+
+  // Index into the array of StaticPrefs
+  const WebIDLPrefIndex prefIndex;
+
+  // Bitmask of global names that we should not be exposed in.
+  const uint16_t nonExposedGlobals : GlobalNames::kCount;
+
+  // A boolean indicating whether a Secure Context is required.
+  const uint16_t secureContext : 1;
+
+  // An origin trial controlling the feature. This can be made a bitfield too if
+  // needed.
+  const OriginTrial trial;
+
+  // A function pointer to a function that can say the property is disabled
+  // even if "enabled" is set to true.  If the pointer is null the value of
+  // "enabled" is used as-is.
+  const PropertyEnabled enabledFunc;
+};
+
+template <typename T>
+struct Prefable {
+  inline bool isEnabled(JSContext* cx, JS::Handle<JSObject*> obj) const {
+    MOZ_ASSERT(!js::IsWrapper(obj));
+    if (MOZ_LIKELY(!disablers)) {
+      return true;
+    }
+    return disablers->isEnabled(cx, obj);
+  }
+
+  // Things that can disable this set of specs. |nullptr| means "cannot be
+  // disabled".
+  const PrefableDisablers* const disablers;
+
+  // Array of specs, terminated in whatever way is customary for T.
+  // Null to indicate a end-of-array for Prefable, when such an
+  // indicator is needed.
+  const T* const specs;
+};
+
+enum PropertyType {
+  eStaticMethod,
+  eStaticAttribute,
+  eMethod,
+  eAttribute,
+  eUnforgeableMethod,
+  eUnforgeableAttribute,
+  eConstant,
+  ePropertyTypeCount
+};
+
+#define NUM_BITS_PROPERTY_INFO_TYPE 3
+#define NUM_BITS_PROPERTY_INFO_PREF_INDEX 13
+#define NUM_BITS_PROPERTY_INFO_SPEC_INDEX 16
+
+struct PropertyInfo {
+ private:
+  // MSVC generates static initializers if we store a jsid here, even if
+  // PropertyInfo has a constexpr constructor. See bug 1460341 and bug 1464036.
+  uintptr_t mIdBits;
+
+ public:
+  // One of PropertyType, will be used for accessing the corresponding Duo in
+  // NativePropertiesN.duos[].
+  uint32_t type : NUM_BITS_PROPERTY_INFO_TYPE;
+  // The index to the corresponding Preable in Duo.mPrefables[].
+  uint32_t prefIndex : NUM_BITS_PROPERTY_INFO_PREF_INDEX;
+  // The index to the corresponding spec in Duo.mPrefables[prefIndex].specs[].
+  uint32_t specIndex : NUM_BITS_PROPERTY_INFO_SPEC_INDEX;
+
+  void SetId(jsid aId) {
+    static_assert(sizeof(jsid) == sizeof(mIdBits),
+                  "jsid should fit in mIdBits");
+    mIdBits = aId.asRawBits();
+  }
+  MOZ_ALWAYS_INLINE jsid Id() const { return jsid::fromRawBits(mIdBits); }
+
+  bool IsStaticMethod() const { return type == eStaticMethod; }
+
+  static int Compare(const PropertyInfo& aInfo1, const PropertyInfo& aInfo2) {
+    // IdToIndexComparator needs to be updated if the order here is changed!
+    if (MOZ_UNLIKELY(aInfo1.mIdBits == aInfo2.mIdBits)) {
+      MOZ_ASSERT((aInfo1.type == eMethod || aInfo1.type == eStaticMethod) &&
+                 (aInfo2.type == eMethod || aInfo2.type == eStaticMethod));
+
+      bool isStatic1 = aInfo1.IsStaticMethod();
+
+      MOZ_ASSERT(isStatic1 != aInfo2.IsStaticMethod(),
+                 "We shouldn't have 2 static methods with the same name!");
+
+      return isStatic1 ? -1 : 1;
+    }
+
+    return aInfo1.mIdBits < aInfo2.mIdBits ? -1 : 1;
+  }
+};
+
+static_assert(
+    ePropertyTypeCount <= 1ull << NUM_BITS_PROPERTY_INFO_TYPE,
+    "We have property type count that is > (1 << NUM_BITS_PROPERTY_INFO_TYPE)");
+
+// Conceptually, NativeProperties has seven (Prefable<T>*, PropertyInfo*) duos
+// (where T is one of JSFunctionSpec, JSPropertySpec, or ConstantSpec), one for
+// each of: static methods and attributes, methods and attributes, unforgeable
+// methods and attributes, and constants.
+//
+// That's 14 pointers, but in most instances most of the duos are all null, and
+// there are many instances. To save space we use a variable-length type,
+// NativePropertiesN<N>, to hold the data and getters to access it. It has N
+// actual duos (stored in duos[]), plus four bits for each of the 7 possible
+// duos: 1 bit that states if that duo is present, and 3 that state that duo's
+// offset (if present) in duos[].
+//
+// All duo accesses should be done via the getters, which contain assertions
+// that check we don't overrun the end of the struct. (The duo data members are
+// public only so they can be statically initialized.) These assertions should
+// never fail so long as (a) accesses to the variable-length part are guarded by
+// appropriate Has*() calls, and (b) all instances are well-formed, i.e. the
+// value of N matches the number of mHas* members that are true.
+//
+// We store all the property ids a NativePropertiesN owns in a single array of
+// PropertyInfo structs. Each struct contains an id and the information needed
+// to find the corresponding Prefable for the enabled check, as well as the
+// information needed to find the correct property descriptor in the
+// Prefable. We also store an array of indices into the PropertyInfo array,
+// sorted by bits of the corresponding jsid. Given a jsid, this allows us to
+// binary search for the index of the corresponding PropertyInfo, if any.
+//
+// Finally, we define a typedef of NativePropertiesN<7>, NativeProperties, which
+// we use as a "base" type used to refer to all instances of NativePropertiesN.
+// (7 is used because that's the maximum valid parameter, though any other
+// value 1..6 could also be used.) This is reasonable because of the
+// aforementioned assertions in the getters. Upcast() is used to convert
+// specific instances to this "base" type.
+//
+// An example
+// ----------
+// NativeProperties points to various things, and it can be hard to keep track.
+// The following example shows the layout.
+//
+// Imagine an example interface, with:
+// - 10 properties
+//   - 6 methods, 3 with no disablers struct, 2 sharing the same disablers
+//     struct, 1 using a different disablers struct
+//   - 4 attributes, all with no disablers
+// - The property order is such that those using the same disablers structs are
+//   together. (This is not guaranteed, but it makes the example simpler.)
+//
+// Each PropertyInfo also contain indices into sMethods/sMethods_specs (for
+// method infos) and sAttributes/sAttributes_specs (for attributes), which let
+// them find their spec, but these are not shown.
+//
+//   sNativeProperties             sNativeProperties_        sNativeProperties_
+//   ----                          sortedPropertyIndices[10] propertyInfos[10]
+//   - <several scalar fields>     ----                      ----
+//   - sortedPropertyIndices ----> <10 indices>         +--> 0 info (method)
+//   - duos[2]                     ----                 |    1 info (method)
+//     ----(methods)                                    |    2 info (method)
+//     0 - mPrefables -------> points to sMethods below |    3 info (method)
+//       - mPropertyInfos ------------------------------+    4 info (method)
+//     1 - mPrefables -------> points to sAttributes below   5 info (method)
+//       - mPropertyInfos ---------------------------------> 6 info (attr)
+//     ----                                                  7 info (attr)
+//   ----                                                    8 info (attr)
+//                                                           9 info (attr)
+//                                                           ----
+//
+// sMethods has three entries (excluding the terminator) because there are
+// three disablers structs. The {nullptr,nullptr} serves as the terminator.
+// There are also END terminators within sMethod_specs; the need for these
+// terminators (as opposed to a length) is deeply embedded in SpiderMonkey.
+// Disablers structs are suffixed with the index of the first spec they cover.
+//
+//   sMethods                               sMethods_specs
+//   ----                                   ----
+//   0 - nullptr                     +----> 0 spec
+//     - specs ----------------------+      1 spec
+//   1 - disablers ---> disablers4          2 spec
+//     - specs ------------------------+    3 END
+//   2 - disablers ---> disablers7     +--> 4 spec
+//     - specs ----------------------+      5 spec
+//   3 - nullptr                     |      6 END
+//     - nullptr                     +----> 7 spec
+//   ----                                   8 END
+//
+// sAttributes has a single entry (excluding the terminator) because all of the
+// specs lack disablers.
+//
+//   sAttributes                            sAttributes_specs
+//   ----                                   ----
+//   0 - nullptr                     +----> 0 spec
+//     - specs ----------------------+      1 spec
+//   1 - nullptr                            2 spec
+//     - nullptr                            3 spec
+//   ----                                   4 END
+//                                          ----
+template <int N>
+struct NativePropertiesN {
+  // Duo structs are stored in the duos[] array, and each element in the array
+  // could require a different T. Therefore, we can't use the correct type for
+  // mPrefables. Instead we use void* and cast to the correct type in the
+  // getters.
+  struct Duo {
+    const /*Prefable<const T>*/ void* const mPrefables;
+    PropertyInfo* const mPropertyInfos;
+  };
+
+  constexpr const NativePropertiesN<7>* Upcast() const {
+    return reinterpret_cast<const NativePropertiesN<7>*>(this);
+  }
+
+  const PropertyInfo* PropertyInfos() const { return duos[0].mPropertyInfos; }
+
+#define DO(SpecT, FieldName)                                                 \
+ public:                                                                     \
+  /* The bitfields indicating the duo's presence and (if present) offset. */ \
+  const uint32_t mHas##FieldName##s : 1;                                     \
+  const uint32_t m##FieldName##sOffset : 3;                                  \
+                                                                             \
+ private:                                                                    \
+  const Duo* FieldName##sDuo() const {                                       \
+    MOZ_ASSERT(Has##FieldName##s());                                         \
+    return &duos[m##FieldName##sOffset];                                     \
+  }                                                                          \
+                                                                             \
+ public:                                                                     \
+  bool Has##FieldName##s() const { return mHas##FieldName##s; }              \
+  const Prefable<const SpecT>* FieldName##s() const {                        \
+    return static_cast<const Prefable<const SpecT>*>(                        \
+        FieldName##sDuo()->mPrefables);                                      \
+  }                                                                          \
+  PropertyInfo* FieldName##PropertyInfos() const {                           \
+    return FieldName##sDuo()->mPropertyInfos;                                \
+  }
+
+  DO(JSFunctionSpec, StaticMethod)
+  DO(JSPropertySpec, StaticAttribute)
+  DO(JSFunctionSpec, Method)
+  DO(JSPropertySpec, Attribute)
+  DO(JSFunctionSpec, UnforgeableMethod)
+  DO(JSPropertySpec, UnforgeableAttribute)
+  DO(ConstantSpec, Constant)
+
+#undef DO
+
+  // The index to the iterator method in MethodPropertyInfos() array.
+  const int16_t iteratorAliasMethodIndex;
+  // The number of PropertyInfo structs that the duos manage. This is the total
+  // count across all duos.
+  const uint16_t propertyInfoCount;
+  // The sorted indices array from sorting property ids, which will be used when
+  // we binary search for a property.
+  uint16_t* sortedPropertyIndices;
+
+  const Duo duos[N];
+};
+
+// Ensure the struct has the expected size. The 8 is for the bitfields plus
+// iteratorAliasMethodIndex and idsLength; the rest is for the idsSortedIndex,
+// and duos[].
+static_assert(sizeof(NativePropertiesN<1>) == 8 + 3 * sizeof(void*), "1 size");
+static_assert(sizeof(NativePropertiesN<2>) == 8 + 5 * sizeof(void*), "2 size");
+static_assert(sizeof(NativePropertiesN<3>) == 8 + 7 * sizeof(void*), "3 size");
+static_assert(sizeof(NativePropertiesN<4>) == 8 + 9 * sizeof(void*), "4 size");
+static_assert(sizeof(NativePropertiesN<5>) == 8 + 11 * sizeof(void*), "5 size");
+static_assert(sizeof(NativePropertiesN<6>) == 8 + 13 * sizeof(void*), "6 size");
+static_assert(sizeof(NativePropertiesN<7>) == 8 + 15 * sizeof(void*), "7 size");
+
+// The "base" type.
+typedef NativePropertiesN<7> NativeProperties;
+
+struct NativePropertiesHolder {
+  const NativeProperties* regular;
+  const NativeProperties* chromeOnly;
+  // Points to a static bool that's set to true once the regular and chromeOnly
+  // NativeProperties have been inited. This is a pointer to a bool instead of
+  // a bool value because NativePropertiesHolder is stored by value in
+  // a static const NativePropertyHooks.
+  bool* inited;
+};
+
+struct NativeNamedOrIndexedPropertyHooks {
+  // The hook to call for resolving indexed or named properties.
+  ResolveOwnProperty mResolveOwnProperty;
+  // The hook to call for enumerating indexed or named properties.
+  EnumerateOwnProperties mEnumerateOwnProperties;
+  // The hook to call to delete a named property.  May be null if there are no
+  // named properties or no named property deleter.  On success (true return)
+  // the "found" argument will be set to true if there was in fact such a named
+  // property and false otherwise.  If it's set to false, the caller is expected
+  // to proceed with whatever deletion behavior it would have if there were no
+  // named properties involved at all (i.e. if the hook were null).  If it's set
+  // to true, it will indicate via opresult whether the delete actually
+  // succeeded.
+  DeleteNamedProperty mDeleteNamedProperty;
+};
+
+// Helper structure for Xrays for DOM binding objects. The same instance is used
+// for instances, interface objects and interface prototype objects of a
+// specific interface.
+struct NativePropertyHooks {
+  const NativeNamedOrIndexedPropertyHooks* mIndexedOrNamedNativeProperties;
+
+  // The property arrays for this interface.
+  NativePropertiesHolder mNativeProperties;
+
+  // This will be set to the ID of the interface prototype object for the
+  // interface, if it has one. If it doesn't have one it will be set to
+  // prototypes::id::_ID_Count.
+  prototypes::ID mPrototypeID;
+
+  // This will be set to the ID of the interface object for the interface, if it
+  // has one. If it doesn't have one it will be set to
+  // constructors::id::_ID_Count.
+  constructors::ID mConstructorID;
+
+  // The JSClass to use for expandos on our Xrays.  Can be null, in which case
+  // Xrays will use a default class of their choice.
+  const JSClass* mXrayExpandoClass;
+};
+
+enum DOMObjectType : uint8_t {
+  eInstance,
+  eGlobalInstance,
+  eInterface,
+  eInterfacePrototype,
+  eGlobalInterfacePrototype,
+  eNamespace,
+  eNamedPropertiesObject
+};
+
+inline bool IsInstance(DOMObjectType type) {
+  return type == eInstance || type == eGlobalInstance;
+}
+
+inline bool IsInterfacePrototype(DOMObjectType type) {
+  return type == eInterfacePrototype || type == eGlobalInterfacePrototype;
+}
+
+typedef JSObject* (*AssociatedGlobalGetter)(JSContext* aCx,
+                                            JS::Handle<JSObject*> aObj);
+
+typedef JSObject* (*ProtoGetter)(JSContext* aCx);
+
+/**
+ * Returns a handle to the relevant WebIDL prototype object for the current
+ * compartment global (which may be a handle to null on out of memory).  Once
+ * allocated, the prototype object is guaranteed to exist as long as the global
+ * does, since the global traces its array of WebIDL prototypes and
+ * constructors.
+ */
+typedef JS::Handle<JSObject*> (*ProtoHandleGetter)(JSContext* aCx);
+
+/**
+ * Serializes a WebIDL object for structured cloning.  aObj may not be in the
+ * compartment of aCx in cases when we were working with a cross-compartment
+ * wrapper.  aObj is expected to be an object of the DOMJSClass that we got the
+ * serializer from.
+ */
+typedef bool (*WebIDLSerializer)(JSContext* aCx,
+                                 JSStructuredCloneWriter* aWriter,
+                                 JS::Handle<JSObject*> aObj);
+
+/**
+ * Deserializes a WebIDL object from a structured clone serialization.
+ */
+typedef JSObject* (*WebIDLDeserializer)(JSContext* aCx,
+                                        nsIGlobalObject* aGlobal,
+                                        JSStructuredCloneReader* aReader);
+
+typedef nsWrapperCache* (*WrapperCacheGetter)(JS::Handle<JSObject*> aObj);
+
+// Special JSClass for reflected DOM objects.
+struct DOMJSClass {
+  // It would be nice to just inherit from JSClass, but that precludes pure
+  // compile-time initialization of the form |DOMJSClass = {...};|, since C++
+  // only allows brace initialization for aggregate/POD types.
+  const JSClass mBase;
+
+  // A list of interfaces that this object implements, in order of decreasing
+  // derivedness.
+  const prototypes::ID mInterfaceChain[MAX_PROTOTYPE_CHAIN_LENGTH];
+
+  // We store the DOM object in reserved slot with index DOM_OBJECT_SLOT or in
+  // the proxy private if we use a proxy object.
+  // Sometimes it's an nsISupports and sometimes it's not; this class tells
+  // us which it is.
+  const bool mDOMObjectIsISupports;
+
+  const NativePropertyHooks* mNativeHooks;
+
+  // A callback to find the associated global for our C++ object.  Note that
+  // this is used in cases when that global is _changing_, so it will not match
+  // the global of the JSObject* passed in to this function!
+  AssociatedGlobalGetter mGetAssociatedGlobal;
+  ProtoHandleGetter mGetProto;
+
+  // This stores the CC participant for the native, null if this class does not
+  // implement cycle collection or if it inherits from nsISupports (we can get
+  // the CC participant by QI'ing in that case).
+  nsCycleCollectionParticipant* mParticipant;
+
+  // The serializer for this class if the relevant object is [Serializable].
+  // Null otherwise.
+  WebIDLSerializer mSerializer;
+
+  // A callback to get the wrapper cache for C++ objects that don't inherit from
+  // nsISupports, or null.
+  WrapperCacheGetter mWrapperCacheGetter;
+
+  static const DOMJSClass* FromJSClass(const JSClass* base) {
+    MOZ_ASSERT(base->flags & JSCLASS_IS_DOMJSCLASS);
+    return reinterpret_cast<const DOMJSClass*>(base);
+  }
+
+  const JSClass* ToJSClass() const { return &mBase; }
+};
+
+// Special JSClass for DOM interface and interface prototype objects.
+struct DOMIfaceAndProtoJSClass {
+  // It would be nice to just inherit from JSClass, but that precludes pure
+  // compile-time initialization of the form
+  // |DOMJSInterfaceAndPrototypeClass = {...};|, since C++ only allows brace
+  // initialization for aggregate/POD types.
+  const JSClass mBase;
+
+  // Either eInterface, eNamespace, eInterfacePrototype,
+  // eGlobalInterfacePrototype or eNamedPropertiesObject.
+  DOMObjectType mType;  // uint8_t
+
+  const prototypes::ID mPrototypeID;  // uint16_t
+  const uint32_t mDepth;
+
+  const NativePropertyHooks* mNativeHooks;
+
+  ProtoGetter mGetParentProto;
+
+  static const DOMIfaceAndProtoJSClass* FromJSClass(const JSClass* base) {
+    MOZ_ASSERT(base->flags & JSCLASS_IS_DOMIFACEANDPROTOJSCLASS);
+    return reinterpret_cast<const DOMIfaceAndProtoJSClass*>(base);
+  }
+
+  const JSClass* ToJSClass() const { return &mBase; }
+};
+
+// Special JSClass for DOM interface objects.
+struct DOMIfaceJSClass : public DOMIfaceAndProtoJSClass {
+  // Boolean indicating whether this object wants an isInstance property
+  // pointing to InterfaceIsInstance defined on it.  Only ever true for the
+  // eInterface case.
+  bool wantsInterfaceIsInstance;
+
+  // The value to return for Function.prototype.toString on this interface
+  // object.
+  const char* mFunToString;
+
+  static const DOMIfaceJSClass* FromJSClass(const JSClass* base) {
+    const DOMIfaceAndProtoJSClass* clazz =
+        DOMIfaceAndProtoJSClass::FromJSClass(base);
+    MOZ_ASSERT(clazz->mType == eInterface || clazz->mType == eNamespace);
+    return static_cast<const DOMIfaceJSClass*>(clazz);
+  }
+};
+
+class ProtoAndIfaceCache;
+
+inline bool DOMGlobalHasProtoAndIFaceCache(JSObject* global) {
+  MOZ_DIAGNOSTIC_ASSERT(JS::GetClass(global)->flags & JSCLASS_DOM_GLOBAL);
+  // This can be undefined if we GC while creating the global
+  return !JS::GetReservedSlot(global, DOM_PROTOTYPE_SLOT).isUndefined();
+}
+
+inline bool HasProtoAndIfaceCache(JSObject* global) {
+  if (!(JS::GetClass(global)->flags & JSCLASS_DOM_GLOBAL)) {
+    return false;
+  }
+  return DOMGlobalHasProtoAndIFaceCache(global);
+}
+
+inline ProtoAndIfaceCache* GetProtoAndIfaceCache(JSObject* global) {
+  MOZ_DIAGNOSTIC_ASSERT(JS::GetClass(global)->flags & JSCLASS_DOM_GLOBAL);
+  return static_cast<ProtoAndIfaceCache*>(
+      JS::GetReservedSlot(global, DOM_PROTOTYPE_SLOT).toPrivate());
+}
+
+}  // namespace mozilla::dom
+
+#endif /* mozilla_dom_DOMJSClass_h */