Bug 1497476 - Remove nsITransferable.kFlavorHasDataProvider. r=NeilDeakin

Depends on D8074

Differential Revision: https://phabricator.services.mozilla.com/D8075

--HG--
extra : moz-landing-system : lando

dom/events/DataTransfer.cpp

@@ -1157,10 +1157,9 @@ DataTransfer::ConvertFromVariant(nsIVariant* aVariant,
 
     nsCOMPtr<nsIFlavorDataProvider> fdp = do_QueryInterface(data);
     if (fdp) {
-      // for flavour data providers, use kFlavorHasDataProvider (which has the
-      // value 0) as the length.
+      // For flavour data providers, use 0 as the length.
       fdp.forget(aSupports);
-      *aLength = nsITransferable::kFlavorHasDataProvider;
+      *aLength = 0;
     } else {
       data.forget(aSupports);
       *aLength = sizeof(nsISupports *);

widget/nsITransferable.idl

@@ -95,8 +95,6 @@ interface nsIFlavorDataProvider : nsISupports
 [scriptable, uuid(97e0c418-1c1e-4106-bad1-9fcb11dff2fe)]
 interface nsITransferable : nsISupports
 {
-  const long kFlavorHasDataProvider = 0;
-
   /**
    * Initializes a transferable object.  This should be called on all
    * transferable objects.  Failure to do so will result in fatal assertions in

widget/nsTransferable.cpp

@@ -262,17 +262,18 @@ nsTransferable::GetTransferData(const char* aFlavor,
       nsCOMPtr<nsISupports> dataBytes;
       uint32_t len;
       data.GetData(getter_AddRefs(dataBytes), &len);
-      if (len == kFlavorHasDataProvider && dataBytes) {
-        // do we have a data provider?
-        nsCOMPtr<nsIFlavorDataProvider> dataProvider =
-          do_QueryInterface(dataBytes);
-        if (dataProvider) {
-          rv = dataProvider->GetFlavorData(
-            this, aFlavor, getter_AddRefs(dataBytes), &len);
-          if (NS_FAILED(rv))
-            break; // the provider failed. fall into the converter code below.
+
+      // Do we have a (lazy) data provider?
+      if (nsCOMPtr<nsIFlavorDataProvider> dataProvider =
+            do_QueryInterface(dataBytes)) {
+        rv = dataProvider->GetFlavorData(this, aFlavor,
+                                         getter_AddRefs(dataBytes), &len);
+        if (NS_FAILED(rv)) {
+          // The provider failed, fall into the converter code below.
+          break;
         }
       }
+
       if (dataBytes && len > 0) { // XXXmats why is zero length not ok?
         *aDataLen = len;
         dataBytes.forget(aData);
@@ -295,17 +296,18 @@ nsTransferable::GetTransferData(const char* aFlavor,
         nsCOMPtr<nsISupports> dataBytes;
         uint32_t len;
         data.GetData(getter_AddRefs(dataBytes), &len);
-        if (len == kFlavorHasDataProvider && dataBytes) {
-          // do we have a data provider?
-          nsCOMPtr<nsIFlavorDataProvider> dataProvider =
-            do_QueryInterface(dataBytes);
-          if (dataProvider) {
-            rv = dataProvider->GetFlavorData(
-              this, aFlavor, getter_AddRefs(dataBytes), &len);
-            if (NS_FAILED(rv))
-              break; // give up
+
+        // Do we have a (lazy) data provider?
+        if (nsCOMPtr<nsIFlavorDataProvider> dataProvider =
+              do_QueryInterface(dataBytes)) {
+          rv = dataProvider->GetFlavorData(this, aFlavor,
+                                           getter_AddRefs(dataBytes), &len);
+          if (NS_FAILED(rv)) {
+            // Give up.
+            break;
           }
         }
+
         mFormatConv->Convert(
           data.GetFlavor().get(), dataBytes, len, aFlavor, aData, aDataLen);
         found = true;