Make HTMLOptionsCollection::mSelect into a strong reference.

The cycle collector makes weak references like this obsolete.

dom/html/HTMLOptionsCollection.cpp

@@ -35,23 +35,8 @@ namespace mozilla {
 namespace dom {
 
 HTMLOptionsCollection::HTMLOptionsCollection(HTMLSelectElement* aSelect)
-{
-  // Do not maintain a reference counted reference. When
-  // the select goes away, it will let us know.
-  mSelect = aSelect;
-}
-
-HTMLOptionsCollection::~HTMLOptionsCollection()
-{
-  DropReference();
-}
-
-void
-HTMLOptionsCollection::DropReference()
-{
-  // Drop our (non ref-counted) reference
-  mSelect = nullptr;
-}
+  : mSelect(aSelect)
+{}
 
 nsresult
 HTMLOptionsCollection::GetOptionIndex(Element* aOption,
@@ -88,7 +73,9 @@ HTMLOptionsCollection::GetOptionIndex(Element* aOption,
 }
 
 
-NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(HTMLOptionsCollection, mElements)
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(HTMLOptionsCollection,
+                                      mElements,
+                                      mSelect)
 
 // nsISupports
 
@@ -124,10 +111,6 @@ HTMLOptionsCollection::GetLength(uint32_t* aLength)
 NS_IMETHODIMP
 HTMLOptionsCollection::SetLength(uint32_t aLength)
 {
-  if (!mSelect) {
-    return NS_ERROR_UNEXPECTED;
-  }
-
   return mSelect->SetLength(aLength);
 }
 
@@ -135,10 +118,6 @@ NS_IMETHODIMP
 HTMLOptionsCollection::SetOption(uint32_t aIndex,
                                  nsIDOMHTMLOptionElement* aOption)
 {
-  if (!mSelect) {
-    return NS_OK;
-  }
-
   // if the new option is null, just remove this option.  Note that it's safe
   // to pass a too-large aIndex in here.
   if (!aOption) {
@@ -187,11 +166,6 @@ HTMLOptionsCollection::SetOption(uint32_t aIndex,
 int32_t
 HTMLOptionsCollection::GetSelectedIndex(ErrorResult& aError)
 {
-  if (!mSelect) {
-    aError.Throw(NS_ERROR_UNEXPECTED);
-    return 0;
-  }
-
   int32_t selectedIndex;
   aError = mSelect->GetSelectedIndex(&selectedIndex);
   return selectedIndex;
@@ -209,11 +183,6 @@ void
 HTMLOptionsCollection::SetSelectedIndex(int32_t aSelectedIndex,
                                         ErrorResult& aError)
 {
-  if (!mSelect) {
-    aError.Throw(NS_ERROR_UNEXPECTED);
-    return;
-  }
-
   aError = mSelect->SetSelectedIndex(aSelectedIndex);
 }
 
@@ -339,22 +308,12 @@ HTMLOptionsCollection::Add(const HTMLOptionOrOptGroupElement& aElement,
                            const Nullable<HTMLElementOrLong>& aBefore,
                            ErrorResult& aError)
 {
-  if (!mSelect) {
-    aError.Throw(NS_ERROR_NOT_INITIALIZED);
-    return;
-  }
-
   mSelect->Add(aElement, aBefore, aError);
 }
 
 void
 HTMLOptionsCollection::Remove(int32_t aIndex, ErrorResult& aError)
 {
-  if (!mSelect) {
-    aError.Throw(NS_ERROR_UNEXPECTED);
-    return;
-  }
-
   uint32_t len = 0;
   mSelect->GetLength(&len);
   if (aIndex < 0 || (uint32_t)aIndex >= len)