diff --git a/content/html/content/public/HTMLCanvasElement.h b/content/html/content/public/HTMLCanvasElement.h
index c6968002ee41..b5d387541240 100644
--- a/content/html/content/public/HTMLCanvasElement.h
+++ b/content/html/content/public/HTMLCanvasElement.h
@@ -83,18 +83,15 @@ public:
              JS::Handle<JS::Value> aContextOptions,
              ErrorResult& aRv);
   void ToDataURL(JSContext* aCx, const nsAString& aType,
-                 const Optional<JS::Handle<JS::Value> >& aParams,
+                 JS::Handle<JS::Value> aParams,
                  nsAString& aDataURL, ErrorResult& aRv)
   {
-    JS::Handle<JS::Value> params = aParams.WasPassed()
-                                 ? aParams.Value()
-                                 : JS::UndefinedHandleValue;
-    aRv = ToDataURL(aType, params, aCx, aDataURL);
+    aRv = ToDataURL(aType, aParams, aCx, aDataURL);
   }
   void ToBlob(JSContext* aCx,
               FileCallback& aCallback,
               const nsAString& aType,
-              const Optional<JS::Handle<JS::Value> >& aParams,
+              JS::Handle<JS::Value> aParams,
               ErrorResult& aRv);
 
   bool MozOpaque() const
diff --git a/content/html/content/src/HTMLCanvasElement.cpp b/content/html/content/src/HTMLCanvasElement.cpp
index 0ef8b142e904..7bdc4f57a259 100644
--- a/content/html/content/src/HTMLCanvasElement.cpp
+++ b/content/html/content/src/HTMLCanvasElement.cpp
@@ -487,7 +487,7 @@ void
 HTMLCanvasElement::ToBlob(JSContext* aCx,
                           FileCallback& aCallback,
                           const nsAString& aType,
-                          const Optional<JS::Handle<JS::Value> >& aParams,
+                          JS::Handle<JS::Value> aParams,
                           ErrorResult& aRv)
 {
   // do a trust check if this is a write-only canvas
@@ -502,13 +502,9 @@ HTMLCanvasElement::ToBlob(JSContext* aCx,
     return;
   }
 
-  JS::Value encoderOptions = aParams.WasPassed()
-                             ? aParams.Value()
-                             : JS::UndefinedValue();
-
   nsAutoString params;
   bool usingCustomParseOptions;
-  aRv = ParseParams(aCx, type, encoderOptions, params, &usingCustomParseOptions);
+  aRv = ParseParams(aCx, type, aParams, params, &usingCustomParseOptions);
   if (aRv.Failed()) {
     return;
   }
diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index 471c5bc5e95e..af75f5f2cb0b 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -8807,18 +8807,14 @@ nsGlobalWindow::ShowModalDialog(const nsAString& aUrl, nsIVariant* aArgument,
 
 JS::Value
 nsGlobalWindow::ShowModalDialog(JSContext* aCx, const nsAString& aUrl,
-                                const Optional<JS::Handle<JS::Value> >& aArgument,
+                                JS::Handle<JS::Value> aArgument,
                                 const nsAString& aOptions,
                                 ErrorResult& aError)
 {
   nsCOMPtr<nsIVariant> args;
-  if (aArgument.WasPassed()) {
-    aError = nsContentUtils::XPConnect()->JSToVariant(aCx,
-                                                      aArgument.Value(),
-                                                      getter_AddRefs(args));
-  } else {
-    args = CreateVoidVariant();
-  }
+  aError = nsContentUtils::XPConnect()->JSToVariant(aCx,
+                                                    aArgument,
+                                                    getter_AddRefs(args));
 
   nsCOMPtr<nsIVariant> retVal = ShowModalDialog(aUrl, args, aOptions, aError);
   if (aError.Failed()) {
diff --git a/dom/base/nsGlobalWindow.h b/dom/base/nsGlobalWindow.h
index 62536d82985a..bc52f49b959c 100644
--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -824,7 +824,7 @@ public:
   void Prompt(const nsAString& aMessage, const nsAString& aInitial,
               nsAString& aReturn, mozilla::ErrorResult& aError);
   void Print(mozilla::ErrorResult& aError);
-  JS::Value ShowModalDialog(JSContext* aCx, const nsAString& aUrl, const mozilla::dom::Optional<JS::Handle<JS::Value> >& aArgument, const nsAString& aOptions, mozilla::ErrorResult& aError);
+  JS::Value ShowModalDialog(JSContext* aCx, const nsAString& aUrl, JS::Handle<JS::Value> aArgument, const nsAString& aOptions, mozilla::ErrorResult& aError);
   void PostMessageMoz(JSContext* aCx, JS::Handle<JS::Value> aMessage,
                       const nsAString& aTargetOrigin,
                       const mozilla::dom::Optional<mozilla::dom::Sequence<JS::Value > >& aTransfer,
diff --git a/dom/bindings/BindingDeclarations.h b/dom/bindings/BindingDeclarations.h
index af017319c7ca..91ed3ba97e6a 100644
--- a/dom/bindings/BindingDeclarations.h
+++ b/dom/bindings/BindingDeclarations.h
@@ -241,32 +241,14 @@ public:
   }
 };
 
-// A specialization of Optional for JS::Value to make sure that when someone
-// calls Construct() on it we will pre-initialized the JS::Value to
-// JS::UndefinedValue() so it can be traced safely.
+// A specialization of Optional for JS::Value to make sure no one ever uses it.
 template<>
-class Optional<JS::Value> : public Optional_base<JS::Value, JS::Value>
+class Optional<JS::Value>
 {
-public:
-  Optional() :
-    Optional_base<JS::Value, JS::Value>()
-  {}
+private:
+  Optional() MOZ_DELETE;
 
-  explicit Optional(JS::Value aValue) :
-    Optional_base<JS::Value, JS::Value>(aValue)
-  {}
-
-  // Don't allow us to have an uninitialized JS::Value
-  void Construct()
-  {
-    Optional_base<JS::Value, JS::Value>::Construct(JS::UndefinedValue());
-  }
-
-  template <class T1>
-  void Construct(const T1& t1)
-  {
-    Optional_base<JS::Value, JS::Value>::Construct(t1);
-  }
+  explicit Optional(JS::Value aValue) MOZ_DELETE;
 };
 
 // A specialization of Optional for NonNull that lets us get a T& from Value()
diff --git a/dom/bindings/Codegen.py b/dom/bindings/Codegen.py
index b3616efc6743..897afd446b4f 100644
--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -11,7 +11,7 @@ import string
 import math
 import itertools
 
-from WebIDL import BuiltinTypes, IDLBuiltinType, IDLNullValue, IDLSequenceType, IDLType, IDLAttribute
+from WebIDL import BuiltinTypes, IDLBuiltinType, IDLNullValue, IDLSequenceType, IDLType, IDLAttribute, IDLUndefinedValue
 from Configuration import NoSuchDescriptorError, getTypesFromDescriptor, getTypesFromDictionary, getTypesFromCallback, Descriptor
 
 AUTOGENERATED_WARNING_COMMENT = \
@@ -3844,21 +3844,22 @@ for (uint32_t i = 0; i < length; ++i) {
             declType = "JS::Value"
         else:
             assert not isMember
-            if isOptional:
-                # We have a specialization of Optional that will use a
-                # Rooted for the storage here.
-                declType = "JS::Handle<JS::Value>"
-            else:
-                declType = "JS::Rooted<JS::Value>"
+            declType = "JS::Rooted<JS::Value>"
             declArgs = "cx"
 
+        assert not isOptional
         templateBody = "${declName} = ${val};"
-        nullHandling = "${declName} = JS::NullValue()"
-
-        templateBody = handleDefaultNull(templateBody, nullHandling)
+        # We may not have a default value if we're being converted for
+        # a setter, say.
+        if defaultValue:
+            if isinstance(defaultValue, IDLNullValue):
+                defaultHandling = "${declName} = JS::NullValue()"
+            else:
+                assert isinstance(defaultValue, IDLUndefinedValue)
+                defaultHandling = "${declName} = JS::UndefinedValue()"
+            templateBody = handleDefault(templateBody, defaultHandling)
         return JSToNativeConversionInfo(templateBody,
                                         declType=CGGeneric(declType),
-                                        dealWithOptional=isOptional,
                                         declArgs=declArgs)
 
     if type.isObject():
@@ -4142,6 +4143,8 @@ def instantiateJSToNativeConversion(info, replacements, checkForValue=False):
 def convertConstIDLValueToJSVal(value):
     if isinstance(value, IDLNullValue):
         return "JS::NullValue()"
+    if isinstance(value, IDLUndefinedValue):
+        return "JS::UndefinedValue()"
     tag = value.type.tag()
     if tag in [IDLType.Tags.int8, IDLType.Tags.uint8, IDLType.Tags.int16,
                IDLType.Tags.uint16, IDLType.Tags.int32]:
diff --git a/dom/bindings/parser/WebIDL.py b/dom/bindings/parser/WebIDL.py
index ef2b8e99a3d6..165eff9e0c5a 100644
--- a/dom/bindings/parser/WebIDL.py
+++ b/dom/bindings/parser/WebIDL.py
@@ -2531,7 +2531,24 @@ class IDLNullValue(IDLObject):
 
     def _getDependentObjects(self):
         return set()
-  
+
+class IDLUndefinedValue(IDLObject):
+    def __init__(self, location):
+        IDLObject.__init__(self, location)
+        self.type = None
+        self.value = None
+
+    def coerceToType(self, type, location):
+        if not type.isAny():
+            raise WebIDLError("Cannot coerce undefined value to type %s." % type,
+                              [location])
+
+        undefinedValue = IDLUndefinedValue(self.location)
+        undefinedValue.type = type
+        return undefinedValue
+
+    def _getDependentObjects(self):
+        return set()
 
 class IDLInterfaceMember(IDLObjectWithIdentifier):
 
@@ -2909,6 +2926,22 @@ class IDLArgument(IDLObjectWithIdentifier):
             # Default optional dictionaries to null, for simplicity,
             # so the codegen doesn't have to special-case this.
             self.defaultValue = IDLNullValue(self.location)
+        elif self.type.isAny():
+            assert (self.defaultValue is None or
+                    isinstance(self.defaultValue, IDLNullValue))
+            if (self.optional and not self.variadic and
+                not self.dictionaryMember and not self.defaultValue):
+                raise WebIDLError("Arguments of type 'any' are always optional "
+                                  "and shouldn't have the 'optional' keyword "
+                                  "unless they're being given a default value "
+                                  "of 'null'",
+                                  [self.location])
+            # 'any' values are always optional.
+            self.optional = True
+            if not self.defaultValue and not self.variadic:
+                # Set the default value to undefined, for simplicity, so the
+                # codegen doesn't have to special-case this.
+                self.defaultValue = IDLUndefinedValue(self.location)
 
         # Now do the coercing thing; this needs to happen after the
         # above creation of a default value.
@@ -4288,6 +4321,10 @@ class Parser(Tokenizer):
             raise WebIDLError("Mandatory arguments can't have a default value.",
                               [self.getLocation(p, 6)])
 
+        # We can't test t.isAny() here and force optional to true, since at this
+        # point t is not a fully resolved type yet (e.g. it might be a typedef).
+        # We'll handle the 'any' case in IDLArgument.complete.
+
         if variadic:
             if optional:
                 raise WebIDLError("Variadic arguments should not be marked optional.",
diff --git a/dom/bindings/parser/tests/test_method.py b/dom/bindings/parser/tests/test_method.py
index 43fa2828b664..5f80b52d60dc 100644
--- a/dom/bindings/parser/tests/test_method.py
+++ b/dom/bindings/parser/tests/test_method.py
@@ -112,7 +112,7 @@ def WebIDLTest(parser, harness):
     checkMethod(methods[11], "::TestMethods::setAny",
                 "setAny",
        [("Void",
-        [("::TestMethods::setAny::arg1", "arg1", "Any", False, False)])])
+        [("::TestMethods::setAny::arg1", "arg1", "Any", True, False)])])
     checkMethod(methods[12], "::TestMethods::doFloats",
                 "doFloats",
        [("Float",
diff --git a/dom/bindings/test/TestBindingHeader.h b/dom/bindings/test/TestBindingHeader.h
index 40c99e89be2d..a666b8c63545 100644
--- a/dom/bindings/test/TestBindingHeader.h
+++ b/dom/bindings/test/TestBindingHeader.h
@@ -146,11 +146,11 @@ public:
   already_AddRefed<TestInterface> Test2(const GlobalObject&,
                                         JSContext*,
                                         const DictForConstructor&,
-                                        JS::Value,
+                                        JS::Handle<JS::Value>,
                                         JS::Handle<JSObject*>,
                                         JS::Handle<JSObject*>,
                                         const Sequence<Dict>&,
-                                        const Optional<JS::Handle<JS::Value> >&,
+                                        JS::Handle<JS::Value>,
                                         const Optional<JS::Handle<JSObject*> >&,
                                         const Optional<JS::Handle<JSObject*> >&,
                                         ErrorResult&);
@@ -466,7 +466,6 @@ public:
   // Any types
   void PassAny(JSContext*, JS::Handle<JS::Value>);
   void PassVariadicAny(JSContext*, const Sequence<JS::Value>&);
-  void PassOptionalAny(JSContext*, const Optional<JS::Handle<JS::Value> >&);
   void PassAnyDefaultNull(JSContext*, JS::Handle<JS::Value>);
   void PassSequenceOfAny(JSContext*, const Sequence<JS::Value>&);
   void PassNullableSequenceOfAny(JSContext*, const Nullable<Sequence<JS::Value> >&);
diff --git a/dom/bindings/test/TestCodeGen.webidl b/dom/bindings/test/TestCodeGen.webidl
index caa6bb4fa95e..eff63176110d 100644
--- a/dom/bindings/test/TestCodeGen.webidl
+++ b/dom/bindings/test/TestCodeGen.webidl
@@ -110,7 +110,8 @@ interface OnlyForUseInConstructor {
  NamedConstructor=Test,
  NamedConstructor=Test(DOMString str),
  NamedConstructor=Test2(DictForConstructor dict, any any1, object obj1,
-                        object? obj2, sequence<Dict> seq, optional any any2,
+                        object? obj2, sequence<Dict> seq,
+                        optional any any2 = null,
                         optional object obj3, optional object? obj4)
  ]
 interface TestInterface {
@@ -428,7 +429,6 @@ interface TestInterface {
   // Any types
   void passAny(any arg);
   void passVariadicAny(any... arg);
-  void passOptionalAny(optional any arg);
   void passAnyDefaultNull(optional any arg = null);
   void passSequenceOfAny(sequence<any> arg);
   void passNullableSequenceOfAny(sequence<any>? arg);
diff --git a/dom/bindings/test/TestExampleGen.webidl b/dom/bindings/test/TestExampleGen.webidl
index e49670215b2a..2b80d165d8eb 100644
--- a/dom/bindings/test/TestExampleGen.webidl
+++ b/dom/bindings/test/TestExampleGen.webidl
@@ -12,7 +12,8 @@
  NamedConstructor=Example,
  NamedConstructor=Example(DOMString str),
  NamedConstructor=Example2(DictForConstructor dict, any any1, object obj1,
-                           object? obj2, sequence<Dict> seq, optional any any2,
+                           object? obj2, sequence<Dict> seq,
+                           optional any any2 = null,
                            optional object obj3, optional object? obj4)
  ]
 interface TestExampleInterface {
@@ -321,7 +322,6 @@ interface TestExampleInterface {
   // Any types
   void passAny(any arg);
   void passVariadicAny(any... arg);
-  void passOptionalAny(optional any arg);
   void passAnyDefaultNull(optional any arg = null);
   void passSequenceOfAny(sequence<any> arg);
   void passNullableSequenceOfAny(sequence<any>? arg);
diff --git a/dom/bindings/test/TestJSImplGen.webidl b/dom/bindings/test/TestJSImplGen.webidl
index ed65db50cfa6..e59dd88163ac 100644
--- a/dom/bindings/test/TestJSImplGen.webidl
+++ b/dom/bindings/test/TestJSImplGen.webidl
@@ -23,7 +23,7 @@ enum MyTestEnum {
              TestInterface? iface, long arg1,
              DictForConstructor dict, any any1,
              object obj1,
-             object? obj2, sequence<Dict> seq, optional any any2,
+             object? obj2, sequence<Dict> seq, optional any any2 = null,
              optional object obj3,
              optional object? obj4),
  JSImplementation="@mozilla.org/test-js-impl-interface;1"]
@@ -344,7 +344,6 @@ interface TestJSImplInterface {
   // Any types
   void passAny(any arg);
   void passVariadicAny(any... arg);
-  void passOptionalAny(optional any arg);
   void passAnyDefaultNull(optional any arg = null);
   void passSequenceOfAny(sequence<any> arg);
   void passNullableSequenceOfAny(sequence<any>? arg);
diff --git a/dom/events/nsDOMMessageEvent.cpp b/dom/events/nsDOMMessageEvent.cpp
index cde017ea5359..76eac5fc5340 100644
--- a/dom/events/nsDOMMessageEvent.cpp
+++ b/dom/events/nsDOMMessageEvent.cpp
@@ -130,9 +130,7 @@ nsDOMMessageEvent::Constructor(const mozilla::dom::GlobalObject& aGlobal,
   bool trusted = event->Init(t);
   event->SetTrusted(trusted);
 
-  if (aParam.mData.WasPassed()) {
-    event->mData = aParam.mData.Value();
-  }
+  event->mData = aParam.mData;
 
   mozilla::HoldJSObjects(event.get());
 
diff --git a/dom/imptests/html/dom/test_interfaces.html b/dom/imptests/html/dom/test_interfaces.html
index 2bc96ed11b83..576ade3025c9 100644
--- a/dom/imptests/html/dom/test_interfaces.html
+++ b/dom/imptests/html/dom/test_interfaces.html
@@ -79,7 +79,7 @@ dictionary EventInit {
 interface CustomEvent : Event {
   readonly attribute any detail;
 
-  void initCustomEvent(DOMString type, boolean bubbles, boolean cancelable, any details);
+  void initCustomEvent(DOMString type, boolean bubbles, boolean cancelable, optional any details);
 };
 
 dictionary CustomEventInit : EventInit {
diff --git a/dom/indexedDB/IDBCursor.cpp b/dom/indexedDB/IDBCursor.cpp
index 31bfb32680ec..28dce0668398 100644
--- a/dom/indexedDB/IDBCursor.cpp
+++ b/dom/indexedDB/IDBCursor.cpp
@@ -697,16 +697,14 @@ IDBCursor::GetValue(JSContext* aCx, ErrorResult& aRv)
 
 void
 IDBCursor::Continue(JSContext* aCx,
-                    const Optional<JS::Handle<JS::Value> >& aKey,
+                    JS::Handle<JS::Value> aKey,
                     ErrorResult &aRv)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
   Key key;
-  if (aKey.WasPassed()) {
-    aRv = key.SetFromJSVal(aCx, aKey.Value());
-    ENSURE_SUCCESS_VOID(aRv);
-  }
+  aRv = key.SetFromJSVal(aCx, aKey);
+  ENSURE_SUCCESS_VOID(aRv);
 
   if (!key.IsUnset()) {
     switch (mDirection) {
@@ -809,9 +807,7 @@ IDBCursor::Update(JSContext* aCx, JS::Handle<JS::Value> aValue,
       return nullptr;
     }
 
-    JS::Rooted<JS::Value> value(aCx, aValue);
-    Optional<JS::Handle<JS::Value> > keyValue(aCx);
-    request = mObjectStore->Put(aCx, value, keyValue, aRv);
+    request = mObjectStore->Put(aCx, aValue, JS::UndefinedHandleValue, aRv);
     if (aRv.Failed()) {
       return nullptr;
     }
@@ -821,9 +817,7 @@ IDBCursor::Update(JSContext* aCx, JS::Handle<JS::Value> aValue,
     aRv = objectKey.ToJSVal(aCx, &keyVal);
     ENSURE_SUCCESS(aRv, nullptr);
 
-    JS::Rooted<JS::Value> value(aCx, aValue);
-    Optional<JS::Handle<JS::Value> > keyValue(aCx, keyVal);
-    request = mObjectStore->Put(aCx, value, keyValue, aRv);
+    request = mObjectStore->Put(aCx, aValue, keyVal, aRv);
     if (aRv.Failed()) {
       return nullptr;
     }
diff --git a/dom/indexedDB/IDBCursor.h b/dom/indexedDB/IDBCursor.h
index b23417db883e..1f17d27de107 100644
--- a/dom/indexedDB/IDBCursor.h
+++ b/dom/indexedDB/IDBCursor.h
@@ -197,8 +197,7 @@ public:
   Advance(uint32_t aCount, ErrorResult& aRv);
 
   void
-  Continue(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
-           ErrorResult& aRv);
+  Continue(JSContext* aCx, JS::Handle<JS::Value> aKey, ErrorResult& aRv);
 
   already_AddRefed<IDBRequest>
   Delete(JSContext* aCx, ErrorResult& aRv);
diff --git a/dom/indexedDB/IDBIndex.cpp b/dom/indexedDB/IDBIndex.cpp
index 0101a4edd9e5..1b610e524881 100644
--- a/dom/indexedDB/IDBIndex.cpp
+++ b/dom/indexedDB/IDBIndex.cpp
@@ -896,7 +896,7 @@ IDBIndex::GetKey(JSContext* aCx, JS::Handle<JS::Value> aKey, ErrorResult& aRv)
 }
 
 already_AddRefed<IDBRequest>
-IDBIndex::GetAll(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
+IDBIndex::GetAll(JSContext* aCx, JS::Handle<JS::Value> aKey,
                  const Optional<uint32_t>& aLimit, ErrorResult& aRv)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
@@ -908,10 +908,8 @@ IDBIndex::GetAll(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
   }
 
   nsRefPtr<IDBKeyRange> keyRange;
-  if (aKey.WasPassed()) {
-    aRv = IDBKeyRange::FromJSVal(aCx, aKey.Value(), getter_AddRefs(keyRange));
-    ENSURE_SUCCESS(aRv, nullptr);
-  }
+  aRv = IDBKeyRange::FromJSVal(aCx, aKey, getter_AddRefs(keyRange));
+  ENSURE_SUCCESS(aRv, nullptr);
 
   uint32_t limit = UINT32_MAX;
   if (aLimit.WasPassed() && aLimit.Value() > 0) {
@@ -923,7 +921,7 @@ IDBIndex::GetAll(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
 
 already_AddRefed<IDBRequest>
 IDBIndex::GetAllKeys(JSContext* aCx,
-                     const Optional<JS::Handle<JS::Value> >& aKey,
+                     JS::Handle<JS::Value> aKey,
                      const Optional<uint32_t>& aLimit, ErrorResult& aRv)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
@@ -935,10 +933,8 @@ IDBIndex::GetAllKeys(JSContext* aCx,
   }
 
   nsRefPtr<IDBKeyRange> keyRange;
-  if (aKey.WasPassed()) {
-    aRv = IDBKeyRange::FromJSVal(aCx, aKey.Value(), getter_AddRefs(keyRange));
-    ENSURE_SUCCESS(aRv, nullptr);
-  }
+  aRv = IDBKeyRange::FromJSVal(aCx, aKey, getter_AddRefs(keyRange));
+  ENSURE_SUCCESS(aRv, nullptr);
 
   uint32_t limit = UINT32_MAX;
   if (aLimit.WasPassed() && aLimit.Value() > 0) {
@@ -950,7 +946,7 @@ IDBIndex::GetAllKeys(JSContext* aCx,
 
 already_AddRefed<IDBRequest>
 IDBIndex::OpenCursor(JSContext* aCx,
-                     const Optional<JS::Handle<JS::Value> >& aRange,
+                     JS::Handle<JS::Value> aRange,
                      IDBCursorDirection aDirection, ErrorResult& aRv)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
@@ -962,10 +958,8 @@ IDBIndex::OpenCursor(JSContext* aCx,
   }
 
   nsRefPtr<IDBKeyRange> keyRange;
-  if (aRange.WasPassed()) {
-    aRv = IDBKeyRange::FromJSVal(aCx, aRange.Value(), getter_AddRefs(keyRange));
-    ENSURE_SUCCESS(aRv, nullptr);
-  }
+  aRv = IDBKeyRange::FromJSVal(aCx, aRange, getter_AddRefs(keyRange));
+  ENSURE_SUCCESS(aRv, nullptr);
 
   IDBCursor::Direction direction = IDBCursor::ConvertDirection(aDirection);
 
@@ -991,7 +985,7 @@ IDBIndex::OpenCursor(JSContext* aCx,
 
 already_AddRefed<IDBRequest>
 IDBIndex::OpenKeyCursor(JSContext* aCx,
-                        const Optional<JS::Handle<JS::Value> >& aRange,
+                        JS::Handle<JS::Value> aRange,
                         IDBCursorDirection aDirection, ErrorResult& aRv)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
@@ -1003,10 +997,8 @@ IDBIndex::OpenKeyCursor(JSContext* aCx,
   }
 
   nsRefPtr<IDBKeyRange> keyRange;
-  if (aRange.WasPassed()) {
-    aRv = IDBKeyRange::FromJSVal(aCx, aRange.Value(), getter_AddRefs(keyRange));
-    ENSURE_SUCCESS(aRv, nullptr);
-  }
+  aRv = IDBKeyRange::FromJSVal(aCx, aRange, getter_AddRefs(keyRange));
+  ENSURE_SUCCESS(aRv, nullptr);
 
   IDBCursor::Direction direction = IDBCursor::ConvertDirection(aDirection);
 
@@ -1014,7 +1006,7 @@ IDBIndex::OpenKeyCursor(JSContext* aCx,
 }
 
 already_AddRefed<IDBRequest>
-IDBIndex::Count(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
+IDBIndex::Count(JSContext* aCx, JS::Handle<JS::Value> aKey,
                 ErrorResult& aRv)
 {
   IDBTransaction* transaction = mObjectStore->Transaction();
@@ -1024,10 +1016,8 @@ IDBIndex::Count(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
   }
 
   nsRefPtr<IDBKeyRange> keyRange;
-  if (aKey.WasPassed()) {
-    aRv = IDBKeyRange::FromJSVal(aCx, aKey.Value(), getter_AddRefs(keyRange));
-    ENSURE_SUCCESS(aRv, nullptr);
-  }
+  aRv = IDBKeyRange::FromJSVal(aCx, aKey, getter_AddRefs(keyRange));
+  ENSURE_SUCCESS(aRv, nullptr);
 
   return CountInternal(keyRange, aRv);
 }
diff --git a/dom/indexedDB/IDBIndex.h b/dom/indexedDB/IDBIndex.h
index 7cd28c66b2e1..6ab82147d8b4 100644
--- a/dom/indexedDB/IDBIndex.h
+++ b/dom/indexedDB/IDBIndex.h
@@ -194,11 +194,11 @@ public:
   }
 
   already_AddRefed<IDBRequest>
-  OpenCursor(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aRange,
+  OpenCursor(JSContext* aCx, JS::Handle<JS::Value> aRange,
              IDBCursorDirection aDirection, ErrorResult& aRv);
 
   already_AddRefed<IDBRequest>
-  OpenKeyCursor(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aRange,
+  OpenKeyCursor(JSContext* aCx, JS::Handle<JS::Value> aRange,
                 IDBCursorDirection aDirection, ErrorResult& aRv);
 
   already_AddRefed<IDBRequest>
@@ -208,7 +208,7 @@ public:
   GetKey(JSContext* aCx, JS::Handle<JS::Value> aKey, ErrorResult& aRv);
 
   already_AddRefed<IDBRequest>
-  Count(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
+  Count(JSContext* aCx, JS::Handle<JS::Value> aKey,
          ErrorResult& aRv);
 
   void
@@ -219,11 +219,11 @@ public:
   }
 
   already_AddRefed<IDBRequest>
-  GetAll(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
+  GetAll(JSContext* aCx, JS::Handle<JS::Value> aKey,
          const Optional<uint32_t>& aLimit, ErrorResult& aRv);
 
   already_AddRefed<IDBRequest>
-  GetAllKeys(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
+  GetAllKeys(JSContext* aCx, JS::Handle<JS::Value> aKey,
              const Optional<uint32_t>& aLimit, ErrorResult& aRv);
 
 private:
diff --git a/dom/indexedDB/IDBObjectStore.cpp b/dom/indexedDB/IDBObjectStore.cpp
index a88252c2b0d2..0c55426ecc4a 100644
--- a/dom/indexedDB/IDBObjectStore.cpp
+++ b/dom/indexedDB/IDBObjectStore.cpp
@@ -1907,7 +1907,7 @@ IDBObjectStore::GetAddInfo(JSContext* aCx,
 
 already_AddRefed<IDBRequest>
 IDBObjectStore::AddOrPut(JSContext* aCx, JS::Handle<JS::Value> aValue,
-                         const Optional<JS::Handle<JS::Value> >& aKey,
+                         JS::Handle<JS::Value> aKey,
                          bool aOverwrite, ErrorResult& aRv)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
@@ -1922,15 +1922,12 @@ IDBObjectStore::AddOrPut(JSContext* aCx, JS::Handle<JS::Value> aValue,
     return nullptr;
   }
 
-  JS::Rooted<JS::Value> keyval(aCx, aKey.WasPassed() ? aKey.Value()
-                                                     : JSVAL_VOID);
-
   StructuredCloneWriteInfo cloneWriteInfo;
   Key key;
   nsTArray<IndexUpdateInfo> updateInfo;
 
   JS::Rooted<JS::Value> value(aCx, aValue);
-  aRv = GetAddInfo(aCx, value, keyval, cloneWriteInfo, key, updateInfo);
+  aRv = GetAddInfo(aCx, value, aKey, cloneWriteInfo, key, updateInfo);
   if (aRv.Failed()) {
     return nullptr;
   }
@@ -2700,7 +2697,7 @@ IDBObjectStore::Get(JSContext* aCx, JS::Handle<JS::Value> aKey,
 
 already_AddRefed<IDBRequest>
 IDBObjectStore::GetAll(JSContext* aCx,
-                       const Optional<JS::Handle<JS::Value> >& aKey,
+                       JS::Handle<JS::Value> aKey,
                        const Optional<uint32_t>& aLimit, ErrorResult& aRv)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
@@ -2711,10 +2708,8 @@ IDBObjectStore::GetAll(JSContext* aCx,
   }
 
   nsRefPtr<IDBKeyRange> keyRange;
-  if (aKey.WasPassed()) {
-    aRv = IDBKeyRange::FromJSVal(aCx, aKey.Value(), getter_AddRefs(keyRange));
-    ENSURE_SUCCESS(aRv, nullptr);
-  }
+  aRv = IDBKeyRange::FromJSVal(aCx, aKey, getter_AddRefs(keyRange));
+  ENSURE_SUCCESS(aRv, nullptr);
 
   uint32_t limit = UINT32_MAX;
   if (aLimit.WasPassed() && aLimit.Value() != 0) {
@@ -2755,7 +2750,7 @@ IDBObjectStore::Delete(JSContext* aCx, JS::Handle<JS::Value> aKey,
 
 already_AddRefed<IDBRequest>
 IDBObjectStore::OpenCursor(JSContext* aCx,
-                           const Optional<JS::Handle<JS::Value> >& aRange,
+                           JS::Handle<JS::Value> aRange,
                            IDBCursorDirection aDirection, ErrorResult& aRv)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
@@ -2766,10 +2761,8 @@ IDBObjectStore::OpenCursor(JSContext* aCx,
   }
 
   nsRefPtr<IDBKeyRange> keyRange;
-  if (aRange.WasPassed()) {
-    aRv = IDBKeyRange::FromJSVal(aCx, aRange.Value(), getter_AddRefs(keyRange));
-    ENSURE_SUCCESS(aRv, nullptr);
-  }
+  aRv = IDBKeyRange::FromJSVal(aCx, aRange, getter_AddRefs(keyRange));
+  ENSURE_SUCCESS(aRv, nullptr);
 
   IDBCursor::Direction direction = IDBCursor::ConvertDirection(aDirection);
   size_t argDirection = static_cast<size_t>(direction);
@@ -2941,7 +2934,7 @@ IDBObjectStore::DeleteIndex(const nsAString& aName, ErrorResult& aRv)
 
 already_AddRefed<IDBRequest>
 IDBObjectStore::Count(JSContext* aCx,
-                      const Optional<JS::Handle<JS::Value> >& aKey,
+                      JS::Handle<JS::Value> aKey,
                       ErrorResult& aRv)
 {
   if (!mTransaction->IsOpen()) {
@@ -2950,17 +2943,15 @@ IDBObjectStore::Count(JSContext* aCx,
   }
 
   nsRefPtr<IDBKeyRange> keyRange;
-  if (aKey.WasPassed()) {
-    aRv = IDBKeyRange::FromJSVal(aCx, aKey.Value(), getter_AddRefs(keyRange));
-    ENSURE_SUCCESS(aRv, nullptr);
-  }
+  aRv = IDBKeyRange::FromJSVal(aCx, aKey, getter_AddRefs(keyRange));
+  ENSURE_SUCCESS(aRv, nullptr);
 
   return CountInternal(keyRange, aRv);
 }
 
 already_AddRefed<IDBRequest>
 IDBObjectStore::GetAllKeys(JSContext* aCx,
-                           const Optional<JS::Handle<JS::Value>>& aKey,
+                           JS::Handle<JS::Value> aKey,
                            const Optional<uint32_t>& aLimit, ErrorResult& aRv)
 {
   MOZ_ASSERT(NS_IsMainThread());
@@ -2971,10 +2962,8 @@ IDBObjectStore::GetAllKeys(JSContext* aCx,
   }
 
   nsRefPtr<IDBKeyRange> keyRange;
-  if (aKey.WasPassed()) {
-    aRv = IDBKeyRange::FromJSVal(aCx, aKey.Value(), getter_AddRefs(keyRange));
-    ENSURE_SUCCESS(aRv, nullptr);
-  }
+  aRv = IDBKeyRange::FromJSVal(aCx, aKey, getter_AddRefs(keyRange));
+  ENSURE_SUCCESS(aRv, nullptr);
 
   uint32_t limit = UINT32_MAX;
   if (aLimit.WasPassed() && aLimit.Value() != 0) {
@@ -2986,7 +2975,7 @@ IDBObjectStore::GetAllKeys(JSContext* aCx,
 
 already_AddRefed<IDBRequest>
 IDBObjectStore::OpenKeyCursor(JSContext* aCx,
-                              const Optional<JS::Handle<JS::Value>>& aRange,
+                              JS::Handle<JS::Value> aRange,
                               IDBCursorDirection aDirection, ErrorResult& aRv)
 {
   MOZ_ASSERT(NS_IsMainThread());
@@ -2997,10 +2986,8 @@ IDBObjectStore::OpenKeyCursor(JSContext* aCx,
   }
 
   nsRefPtr<IDBKeyRange> keyRange;
-  if (aRange.WasPassed()) {
-    aRv = IDBKeyRange::FromJSVal(aCx, aRange.Value(), getter_AddRefs(keyRange));
-    ENSURE_SUCCESS(aRv, nullptr);
-  }
+  aRv = IDBKeyRange::FromJSVal(aCx, aRange, getter_AddRefs(keyRange));
+  ENSURE_SUCCESS(aRv, nullptr);
 
   IDBCursor::Direction direction = IDBCursor::ConvertDirection(aDirection);
 
diff --git a/dom/indexedDB/IDBObjectStore.h b/dom/indexedDB/IDBObjectStore.h
index 6936f44b9bbb..f0973a7d8809 100644
--- a/dom/indexedDB/IDBObjectStore.h
+++ b/dom/indexedDB/IDBObjectStore.h
@@ -304,7 +304,7 @@ public:
 
   already_AddRefed<IDBRequest>
   Put(JSContext* aCx, JS::Handle<JS::Value> aValue,
-      const Optional<JS::Handle<JS::Value> >& aKey, ErrorResult& aRv)
+      JS::Handle<JS::Value> aKey, ErrorResult& aRv)
   {
     NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
     return AddOrPut(aCx, aValue, aKey, true, aRv);
@@ -312,7 +312,7 @@ public:
 
   already_AddRefed<IDBRequest>
   Add(JSContext* aCx, JS::Handle<JS::Value> aValue,
-      const Optional<JS::Handle<JS::Value> >& aKey, ErrorResult& aRv)
+      JS::Handle<JS::Value> aKey, ErrorResult& aRv)
   {
     NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
     return AddOrPut(aCx, aValue, aKey, false, aRv);
@@ -328,7 +328,7 @@ public:
   Clear(ErrorResult& aRv);
 
   already_AddRefed<IDBRequest>
-  OpenCursor(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aRange,
+  OpenCursor(JSContext* aCx, JS::Handle<JS::Value> aRange,
              IDBCursorDirection aDirection, ErrorResult& aRv);
 
   already_AddRefed<IDBIndex>
@@ -347,19 +347,19 @@ public:
   DeleteIndex(const nsAString& aIndexName, ErrorResult& aRv);
 
   already_AddRefed<IDBRequest>
-  Count(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
+  Count(JSContext* aCx, JS::Handle<JS::Value> aKey,
         ErrorResult& aRv);
 
   already_AddRefed<IDBRequest>
-  GetAll(JSContext* aCx, const Optional<JS::Handle<JS::Value> >& aKey,
+  GetAll(JSContext* aCx, JS::Handle<JS::Value> aKey,
          const Optional<uint32_t>& aLimit, ErrorResult& aRv);
 
   already_AddRefed<IDBRequest>
-  GetAllKeys(JSContext* aCx, const Optional<JS::Handle<JS::Value>>& aKey,
+  GetAllKeys(JSContext* aCx, JS::Handle<JS::Value> aKey,
              const Optional<uint32_t>& aLimit, ErrorResult& aRv);
 
   already_AddRefed<IDBRequest>
-  OpenKeyCursor(JSContext* aCx, const Optional<JS::Handle<JS::Value>>& aRange,
+  OpenKeyCursor(JSContext* aCx, JS::Handle<JS::Value> aRange,
                 IDBCursorDirection aDirection, ErrorResult& aRv);
 
 protected:
@@ -375,7 +375,7 @@ protected:
 
   already_AddRefed<IDBRequest>
   AddOrPut(JSContext* aCx, JS::Handle<JS::Value> aValue,
-           const Optional<JS::Handle<JS::Value> >& aKey, bool aOverwrite,
+           JS::Handle<JS::Value> aKey, bool aOverwrite,
            ErrorResult& aRv);
 
   already_AddRefed<IDBIndex>
diff --git a/dom/promise/Promise.cpp b/dom/promise/Promise.cpp
index 056b4d3667a8..b49998831f59 100644
--- a/dom/promise/Promise.cpp
+++ b/dom/promise/Promise.cpp
@@ -500,13 +500,11 @@ Promise::Constructor(const GlobalObject& aGlobal,
 
 /* static */ already_AddRefed<Promise>
 Promise::Resolve(const GlobalObject& aGlobal, JSContext* aCx,
-                 const Optional<JS::Handle<JS::Value>>& aValue, ErrorResult& aRv)
+                 JS::Handle<JS::Value> aValue, ErrorResult& aRv)
 {
   // If a Promise was passed, just return it.
-  JS::Rooted<JS::Value> value(aCx, aValue.WasPassed() ? aValue.Value() :
-                                                        JS::UndefinedValue());
-  if (value.isObject()) {
-    JS::Rooted<JSObject*> valueObj(aCx, &value.toObject());
+  if (aValue.isObject()) {
+    JS::Rooted<JSObject*> valueObj(aCx, &aValue.toObject());
     Promise* nextPromise;
     nsresult rv = UNWRAP_OBJECT(Promise, valueObj, nextPromise);
 
@@ -525,7 +523,7 @@ Promise::Resolve(const GlobalObject& aGlobal, JSContext* aCx,
     }
   }
 
-  return Resolve(window, aCx, value, aRv);
+  return Resolve(window, aCx, aValue, aRv);
 }
 
 /* static */ already_AddRefed<Promise>
@@ -541,7 +539,7 @@ Promise::Resolve(nsPIDOMWindow* aWindow, JSContext* aCx,
 
 /* static */ already_AddRefed<Promise>
 Promise::Reject(const GlobalObject& aGlobal, JSContext* aCx,
-                const Optional<JS::Handle<JS::Value>>& aValue, ErrorResult& aRv)
+                JS::Handle<JS::Value> aValue, ErrorResult& aRv)
 {
   nsCOMPtr<nsPIDOMWindow> window;
   if (MOZ_LIKELY(NS_IsMainThread())) {
@@ -552,9 +550,7 @@ Promise::Reject(const GlobalObject& aGlobal, JSContext* aCx,
     }
   }
 
-  return Reject(window, aCx,
-                aValue.WasPassed() ? aValue.Value() : JS::UndefinedHandleValue,
-                aRv);
+  return Reject(window, aCx, aValue, aRv);
 }
 
 /* static */ already_AddRefed<Promise>
@@ -736,8 +732,8 @@ Promise::All(const GlobalObject& aGlobal, JSContext* aCx,
       aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
       return nullptr;
     }
-    Optional<JS::Handle<JS::Value>> optValue(aCx, JS::ObjectValue(*empty));
-    return Promise::Resolve(aGlobal, aCx, optValue, aRv);
+    JS::Rooted<JS::Value> value(aCx, JS::ObjectValue(*empty));
+    return Promise::Resolve(aGlobal, aCx, value, aRv);
   }
 
   nsRefPtr<Promise> promise = new Promise(window);
@@ -747,8 +743,8 @@ Promise::All(const GlobalObject& aGlobal, JSContext* aCx,
   nsRefPtr<PromiseCallback> rejectCb = new RejectPromiseCallback(promise);
 
   for (uint32_t i = 0; i < aIterable.Length(); ++i) {
-    Optional<JS::Handle<JS::Value>> optValue(aCx, aIterable.ElementAt(i));
-    nsRefPtr<Promise> nextPromise = Promise::Resolve(aGlobal, aCx, optValue, aRv);
+    JS::Rooted<JS::Value> value(aCx, aIterable.ElementAt(i));
+    nsRefPtr<Promise> nextPromise = Promise::Resolve(aGlobal, aCx, value, aRv);
 
     MOZ_ASSERT(!aRv.Failed());
 
@@ -783,8 +779,8 @@ Promise::Race(const GlobalObject& aGlobal, JSContext* aCx,
   nsRefPtr<PromiseCallback> rejectCb = new RejectPromiseCallback(promise);
 
   for (uint32_t i = 0; i < aIterable.Length(); ++i) {
-    Optional<JS::Handle<JS::Value>> optValue(aCx, aIterable.ElementAt(i));
-    nsRefPtr<Promise> nextPromise = Promise::Resolve(aGlobal, aCx, optValue, aRv);
+    JS::Rooted<JS::Value> value(aCx, aIterable.ElementAt(i));
+    nsRefPtr<Promise> nextPromise = Promise::Resolve(aGlobal, aCx, value, aRv);
     // According to spec, Resolve can throw, but our implementation never does.
     // Well it does when window isn't passed on the main thread, but that is an
     // implementation detail which should never be reached since we are checking
diff --git a/dom/promise/Promise.h b/dom/promise/Promise.h
index 28959dc5ca00..9da9872554c5 100644
--- a/dom/promise/Promise.h
+++ b/dom/promise/Promise.h
@@ -66,7 +66,7 @@ public:
 
   static already_AddRefed<Promise>
   Resolve(const GlobalObject& aGlobal, JSContext* aCx,
-          const Optional<JS::Handle<JS::Value>>& aValue, ErrorResult& aRv);
+          JS::Handle<JS::Value> aValue, ErrorResult& aRv);
 
   static already_AddRefed<Promise>
   Resolve(nsPIDOMWindow* aWindow, JSContext* aCx,
@@ -74,7 +74,7 @@ public:
 
   static already_AddRefed<Promise>
   Reject(const GlobalObject& aGlobal, JSContext* aCx,
-         const Optional<JS::Handle<JS::Value>>& aValue, ErrorResult& aRv);
+         JS::Handle<JS::Value> aValue, ErrorResult& aRv);
 
   static already_AddRefed<Promise>
   Reject(nsPIDOMWindow* aWindow, JSContext* aCx,
diff --git a/dom/webidl/HTMLCanvasElement.webidl b/dom/webidl/HTMLCanvasElement.webidl
index 408fd6e34437..95b2245b96bf 100644
--- a/dom/webidl/HTMLCanvasElement.webidl
+++ b/dom/webidl/HTMLCanvasElement.webidl
@@ -26,11 +26,11 @@ interface HTMLCanvasElement : HTMLElement {
 
   [Throws]
   DOMString toDataURL(optional DOMString type = "",
-                      optional any encoderOptions);
+                      any encoderOptions);
   [Throws]
   void toBlob(FileCallback _callback,
               optional DOMString type = "",
-              optional any encoderOptions);
+              any encoderOptions);
 };
 
 // Mozilla specific bits
diff --git a/dom/webidl/IDBCursor.webidl b/dom/webidl/IDBCursor.webidl
index 6279953393e4..883402df7123 100644
--- a/dom/webidl/IDBCursor.webidl
+++ b/dom/webidl/IDBCursor.webidl
@@ -32,7 +32,7 @@ interface IDBCursor {
     void       advance ([EnforceRange] unsigned long count);
 
     [Throws]
-    void       continue (optional any key);
+    void       continue (any key);
 
     [Throws]
     IDBRequest delete ();
diff --git a/dom/webidl/IDBIndex.webidl b/dom/webidl/IDBIndex.webidl
index 334cc2e66fd3..e828bc217846 100644
--- a/dom/webidl/IDBIndex.webidl
+++ b/dom/webidl/IDBIndex.webidl
@@ -23,10 +23,10 @@ interface IDBIndex {
     readonly    attribute boolean        unique;
 
     [Throws]
-    IDBRequest openCursor (optional any range, optional IDBCursorDirection direction = "next");
+    IDBRequest openCursor (any range, optional IDBCursorDirection direction = "next");
 
     [Throws]
-    IDBRequest openKeyCursor (optional any range, optional IDBCursorDirection direction = "next");
+    IDBRequest openKeyCursor (any range, optional IDBCursorDirection direction = "next");
 
     [Throws]
     IDBRequest get (any key);
@@ -35,15 +35,15 @@ interface IDBIndex {
     IDBRequest getKey (any key);
 
     [Throws]
-    IDBRequest count (optional any key);
+    IDBRequest count (any key);
 };
 
 partial interface IDBIndex {
     readonly attribute DOMString storeName;
 
     [Throws]
-    IDBRequest mozGetAll (optional any key, optional unsigned long limit);
+    IDBRequest mozGetAll (any key, optional unsigned long limit);
 
     [Throws]
-    IDBRequest mozGetAllKeys (optional any key, optional unsigned long limit);
+    IDBRequest mozGetAllKeys (any key, optional unsigned long limit);
 };
diff --git a/dom/webidl/IDBObjectStore.webidl b/dom/webidl/IDBObjectStore.webidl
index d364ea340bc4..8b3a6cbd12b9 100644
--- a/dom/webidl/IDBObjectStore.webidl
+++ b/dom/webidl/IDBObjectStore.webidl
@@ -25,10 +25,10 @@ interface IDBObjectStore {
     readonly    attribute boolean        autoIncrement;
 
     [Throws]
-    IDBRequest put (any value, optional any key);
+    IDBRequest put (any value, any key);
 
     [Throws]
-    IDBRequest add (any value, optional any key);
+    IDBRequest add (any value, any key);
 
     [Throws]
     IDBRequest delete (any key);
@@ -40,7 +40,7 @@ interface IDBObjectStore {
     IDBRequest clear ();
 
     [Throws]
-    IDBRequest openCursor (optional any range, optional IDBCursorDirection direction = "next");
+    IDBRequest openCursor (any range, optional IDBCursorDirection direction = "next");
 
     // Bug 899972
     // IDBIndex   createIndex (DOMString name, (DOMString or sequence<DOMString>) keyPath, optional IDBIndexParameters optionalParameters);
@@ -58,20 +58,20 @@ interface IDBObjectStore {
     void       deleteIndex (DOMString indexName);
 
     [Throws]
-    IDBRequest count (optional any key);
+    IDBRequest count (any key);
 };
 
 partial interface IDBObjectStore {
     // Success fires IDBTransactionEvent, result == array of values for given keys
     [Throws]
-    IDBRequest mozGetAll (optional any key, optional unsigned long limit);
+    IDBRequest mozGetAll (any key, optional unsigned long limit);
 
     [Pref="dom.indexedDB.experimental", Throws]
-    IDBRequest getAll (optional any key, optional unsigned long limit);
+    IDBRequest getAll (any key, optional unsigned long limit);
 
     [Pref="dom.indexedDB.experimental", Throws]
-    IDBRequest getAllKeys (optional any key, optional unsigned long limit);
+    IDBRequest getAllKeys (any key, optional unsigned long limit);
 
     [Pref="dom.indexedDB.experimental", Throws]
-    IDBRequest openKeyCursor (optional any range, optional IDBCursorDirection direction = "next");
+    IDBRequest openKeyCursor (any range, optional IDBCursorDirection direction = "next");
 };
diff --git a/dom/webidl/Promise.webidl b/dom/webidl/Promise.webidl
index f106b6eda3fb..21e00ae3b415 100644
--- a/dom/webidl/Promise.webidl
+++ b/dom/webidl/Promise.webidl
@@ -26,9 +26,9 @@ interface Promise {
   // Promise object in this scope without having resolved the interface object
   // first.
   [NewObject, Throws]
-  static Promise resolve(optional any value);
+  static Promise resolve(any value);
   [NewObject, Throws]
-  static Promise reject(optional any value);
+  static Promise reject(any value);
 
   // The [TreatNonCallableAsNull] annotation is required since then() should do
   // nothing instead of throwing errors when non-callable arguments are passed.
diff --git a/dom/webidl/RTCStatsReport.webidl b/dom/webidl/RTCStatsReport.webidl
index 053dde32e01e..a0479684ce03 100644
--- a/dom/webidl/RTCStatsReport.webidl
+++ b/dom/webidl/RTCStatsReport.webidl
@@ -146,7 +146,7 @@ dictionary RTCStatsReportInternal {
 interface RTCStatsReport {
   [ChromeOnly]
   readonly attribute DOMString mozPcid;
-  void forEach(RTCStatsReportCallback callbackFn, optional any thisArg);
+  void forEach(RTCStatsReportCallback callbackFn, any thisArg);
   object get(DOMString key);
   boolean has(DOMString key);
 };
diff --git a/dom/webidl/TestInterfaceJS.webidl b/dom/webidl/TestInterfaceJS.webidl
index e9e5e2cb9e59..ff5049c22d5a 100644
--- a/dom/webidl/TestInterfaceJS.webidl
+++ b/dom/webidl/TestInterfaceJS.webidl
@@ -6,7 +6,7 @@
 
 [JSImplementation="@mozilla.org/dom/test-interface-js;1",
  Pref="dom.expose_test_interfaces",
- Constructor(optional any anyArg, optional object objectArg)]
+ Constructor(any anyArg, optional object objectArg)]
 interface TestInterfaceJS {
   readonly attribute any anyArg;
   readonly attribute object objectArg;
diff --git a/dom/webidl/Window.webidl b/dom/webidl/Window.webidl
index 41904d0e4b30..f061bc2fd50c 100644
--- a/dom/webidl/Window.webidl
+++ b/dom/webidl/Window.webidl
@@ -74,7 +74,7 @@ typedef any Transferable;
   [Throws] DOMString? prompt(optional DOMString message = "", optional DOMString default = "");
   [Throws] void print();
   //[Throws] any showModalDialog(DOMString url, optional any argument);
-  [Throws] any showModalDialog(DOMString url, optional any argument, optional DOMString options = "");
+  [Throws] any showModalDialog(DOMString url, any argument, optional DOMString options = "");
 
   [Throws, CrossOriginCallable] void postMessage(any message, DOMString targetOrigin, optional sequence<Transferable> transfer);
 
diff --git a/dom/webidl/WorkerConsole.webidl b/dom/webidl/WorkerConsole.webidl
index 0b517cb197ed..0234d0df9ecf 100644
--- a/dom/webidl/WorkerConsole.webidl
+++ b/dom/webidl/WorkerConsole.webidl
@@ -12,12 +12,12 @@ interface WorkerConsole {
   void _exception(any... data);
   void debug(any... data);
   void trace();
-  void dir(optional any data);
+  void dir(any data);
   void group(any... data);
   void groupCollapsed(any... data);
   void groupEnd(any... data);
-  void time(optional any time);
-  void timeEnd(optional any time);
+  void time(any time);
+  void timeEnd(any time);
   void profile(any... data);
   void profileEnd(any... data);
   void assert(boolean condition, any... data);
diff --git a/dom/workers/Console.cpp b/dom/workers/Console.cpp
index 014c8dc5c397..2412e19a88d5 100644
--- a/dom/workers/Console.cpp
+++ b/dom/workers/Console.cpp
@@ -492,14 +492,13 @@ WorkerConsole::Trace(JSContext* aCx)
 }
 
 void
-WorkerConsole::Dir(JSContext* aCx,
-                   const Optional<JS::Handle<JS::Value>>& aValue)
+WorkerConsole::Dir(JSContext* aCx, JS::Handle<JS::Value> aValue)
 {
   Sequence<JS::Value> data;
   SequenceRooter<JS::Value> rooter(aCx, &data);
 
-  if (aValue.WasPassed()) {
-    data.AppendElement(aValue.Value());
+  if (!aValue.isUndefined()) {
+    data.AppendElement(aValue);
   }
 
   Method(aCx, "dir", data, 1);
@@ -510,14 +509,13 @@ METHOD(GroupCollapsed, "groupCollapsed")
 METHOD(GroupEnd, "groupEnd")
 
 void
-WorkerConsole::Time(JSContext* aCx,
-                    const Optional<JS::Handle<JS::Value>>& aTimer)
+WorkerConsole::Time(JSContext* aCx, JS::Handle<JS::Value> aTimer)
 {
   Sequence<JS::Value> data;
   SequenceRooter<JS::Value> rooter(aCx, &data);
 
-  if (aTimer.WasPassed()) {
-    data.AppendElement(aTimer.Value());
+  if (!aTimer.isUndefined()) {
+    data.AppendElement(aTimer);
   }
 
   Method(aCx, "time", data, 1);
@@ -525,13 +523,13 @@ WorkerConsole::Time(JSContext* aCx,
 
 void
 WorkerConsole::TimeEnd(JSContext* aCx,
-                       const Optional<JS::Handle<JS::Value>>& aTimer)
+                       JS::Handle<JS::Value> aTimer)
 {
   Sequence<JS::Value> data;
   SequenceRooter<JS::Value> rooter(aCx, &data);
 
-  if (aTimer.WasPassed()) {
-    data.AppendElement(aTimer.Value());
+  if (!aTimer.isUndefined()) {
+    data.AppendElement(aTimer);
   }
 
   Method(aCx, "timeEnd", data, 1);
diff --git a/dom/workers/Console.h b/dom/workers/Console.h
index ade635caeaa8..cd4c75372fce 100644
--- a/dom/workers/Console.h
+++ b/dom/workers/Console.h
@@ -70,7 +70,7 @@ public:
   Trace(JSContext* aCx);
 
   void
-  Dir(JSContext* aCx, const Optional<JS::Handle<JS::Value>>& aValue);
+  Dir(JSContext* aCx, JS::Handle<JS::Value> aValue);
 
   void
   Group(JSContext* aCx, const Sequence<JS::Value>& aData);
@@ -82,10 +82,10 @@ public:
   GroupEnd(JSContext* aCx, const Sequence<JS::Value>& aData);
 
   void
-  Time(JSContext* aCx, const Optional<JS::Handle<JS::Value>>& aTimer);
+  Time(JSContext* aCx, JS::Handle<JS::Value> aTimer);
 
   void
-  TimeEnd(JSContext* aCx, const Optional<JS::Handle<JS::Value>>& aTimer);
+  TimeEnd(JSContext* aCx, JS::Handle<JS::Value> aTimer);
 
   void
   Profile(JSContext* aCx, const Sequence<JS::Value>& aData);