Bug 1598915 - [1/2] Drive-by cleanup: replace manual pointer-fiddling with RefPtr r=win-reviewers,handyman

`nsDataObj::mTransferable`'s lifecycle and ownership semantics are
trivially that of `RefPtr`. Use it.

(We do not presently extend this to `m_enumFE`, below; according to
comments in IEnumFE.h, that one's less trivial.)

No functional changes.

Differential Revision: https://phabricator.services.mozilla.com/D216624

widget/windows/nsDataObj.cpp

@@ -530,7 +530,7 @@ nsDataObj::nsDataObj(nsIURI* uri)
 // destruction
 //-----------------------------------------------------
 nsDataObj::~nsDataObj() {
-  NS_IF_RELEASE(mTransferable);
+  mTransferable = nullptr;
 
   mDataFlavors.Clear();
 
@@ -774,7 +774,7 @@ STDMETHODIMP nsDataObj::GetData(LPFORMATETC aFormat, LPSTGMEDIUM pSTM) {
           //       ("***** nsDataObj::GetData - Unknown format %u\n", format));
           return GetText(df, *aFormat, *pSTM);
       }  // switch
-    }    // if
+    }  // if
     dfInx++;
   }  // while
 
@@ -1861,16 +1861,7 @@ void nsDataObj::AddDataFlavor(const char* aDataFlavor, LPFORMATETC aFE) {
 // Sets the transferable object
 //-----------------------------------------------------
 void nsDataObj::SetTransferable(nsITransferable* aTransferable) {
-  NS_IF_RELEASE(mTransferable);
-
   mTransferable = aTransferable;
-  if (nullptr == mTransferable) {
-    return;
-  }
-
-  NS_ADDREF(mTransferable);
-
-  return;
 }
 
 //

widget/windows/nsDataObj.h

@@ -166,9 +166,8 @@ class nsDataObj : public IDataObject, public IDataObjectAsyncCapability {
  private:
   nsTArray<nsCString> mDataFlavors;
 
-  nsITransferable* mTransferable;  // nsDataObj owns and ref counts
-                                   // nsITransferable, the nsITransferable does
-                                   // know anything about the nsDataObj
+  // the nsITransferable knows nothing about the nsDataObj
+  RefPtr<nsITransferable> mTransferable;
 
  protected:
   CEnumFormatEtc* m_enumFE;  // Ownership Rules: