diff --git a/widget/gtk/nsClipboardWayland.cpp b/widget/gtk/nsClipboardWayland.cpp

--- a/widget/gtk/nsClipboardWayland.cpp

+++ b/widget/gtk/nsClipboardWayland.cpp

@@ -155,6 +155,8 @@

 }

 bool WaylandDataOffer::RequestDataTransfer(const char* aMimeType, int fd) {

+  LOGCLIP(

+      ("WaylandDataOffer::RequestDataTransfer MIME %s FD %d\n", aMimeType, fd));

   if (mWaylandDataOffer) {

     wl_data_offer_receive(mWaylandDataOffer, aMimeType, fd);

     return true;

@@ -164,6 +166,8 @@

 }

 void WaylandDataOffer::DragOfferAccept(const char* aMimeType, uint32_t aTime) {

+  LOGDRAG(("WaylandDataOffer::DragOfferAccept MIME %s aTime %d\n", aMimeType,

+           aTime));

   wl_data_offer_accept(mWaylandDataOffer, aTime, aMimeType);

 }

@@ -175,6 +179,9 @@

   uint32_t preferredAction = gdk_to_wl_actions(aPreferredAction);

   uint32_t allActions = WL_DATA_DEVICE_MANAGER_DND_ACTION_NONE;

+  LOGDRAG(("WaylandDataOffer::SetDragStatus aPreferredAction %d\n",

+           aPreferredAction));

+

   /* We only don't choose a preferred action if we don't accept any.

    * If we do accept any, it is currently alway copy and move

    */

@@ -412,12 +419,17 @@

 char* nsWaylandDragContext::GetData(const char* aMimeType,

                                     uint32_t* aContentLength) {

+  LOGDRAG(("nsWaylandDragContext::GetData %s\n", aMimeType));

   mDataOffer->DragOfferAccept(aMimeType, mTime);

   return mDataOffer->GetData(mDisplay, aMimeType, aContentLength);

 }

 void nsRetrievalContextWayland::RegisterNewDataOffer(

     wl_data_offer* aWaylandDataOffer) {

+  LOGCLIP(

+      ("nsRetrievalContextWayland::RegisterNewDataOffer (wl_data_offer) %p\n",

+       aWaylandDataOffer));

+

   DataOffer* dataOffer = static_cast<DataOffer*>(

       g_hash_table_lookup(mActiveOffers, aWaylandDataOffer));

   MOZ_ASSERT(

@@ -432,6 +444,9 @@

 void nsRetrievalContextWayland::RegisterNewDataOffer(

     gtk_primary_selection_offer* aPrimaryDataOffer) {

+  LOGCLIP(("nsRetrievalContextWayland::RegisterNewDataOffer (primary) %p\n",

+           aPrimaryDataOffer));

+

   DataOffer* dataOffer = static_cast<DataOffer*>(

       g_hash_table_lookup(mActiveOffers, aPrimaryDataOffer));

   MOZ_ASSERT(

@@ -446,6 +461,9 @@

 void nsRetrievalContextWayland::RegisterNewDataOffer(

     zwp_primary_selection_offer_v1* aPrimaryDataOffer) {

+  LOGCLIP(("nsRetrievalContextWayland::RegisterNewDataOffer (primary ZWP) %p\n",

+           aPrimaryDataOffer));

+

   DataOffer* dataOffer = static_cast<DataOffer*>(

       g_hash_table_lookup(mActiveOffers, aPrimaryDataOffer));

   MOZ_ASSERT(

@@ -460,6 +478,10 @@

 void nsRetrievalContextWayland::SetClipboardDataOffer(

     wl_data_offer* aWaylandDataOffer) {

+  LOGCLIP(

+      ("nsRetrievalContextWayland::SetClipboardDataOffer (wl_data_offer) %p\n",

+       aWaylandDataOffer));

+

   // Delete existing clipboard data offer

   mClipboardOffer = nullptr;

@@ -468,7 +490,11 @@

   if (aWaylandDataOffer != nullptr) {

     DataOffer* dataOffer = static_cast<DataOffer*>(

         g_hash_table_lookup(mActiveOffers, aWaylandDataOffer));

-    NS_ASSERTION(dataOffer, "We're missing stored clipboard data offer!");

+#ifdef MOZ_LOGGING

+    if (!dataOffer) {

+      LOGCLIP(("    We're missing stored clipboard data offer!\n"));

+    }

+#endif

     if (dataOffer) {

       g_hash_table_remove(mActiveOffers, aWaylandDataOffer);

       mClipboardOffer = WrapUnique(dataOffer);

@@ -478,6 +504,9 @@

 void nsRetrievalContextWayland::SetPrimaryDataOffer(

     gtk_primary_selection_offer* aPrimaryDataOffer) {

+  LOGCLIP(("nsRetrievalContextWayland::SetPrimaryDataOffer (primary) %p\n",

+           aPrimaryDataOffer));

+

   // Release any primary offer we have.

   mPrimaryOffer = nullptr;

@@ -486,7 +515,11 @@

   if (aPrimaryDataOffer) {

     DataOffer* dataOffer = static_cast<DataOffer*>(

         g_hash_table_lookup(mActiveOffers, aPrimaryDataOffer));

-    NS_ASSERTION(dataOffer, "We're missing primary data offer!");

+#ifdef MOZ_LOGGING

+    if (!dataOffer) {

+      LOGCLIP(("    We're missing stored primary data offer!\n"));

+    }

+#endif

     if (dataOffer) {

       g_hash_table_remove(mActiveOffers, aPrimaryDataOffer);

       mPrimaryOffer = WrapUnique(dataOffer);

@@ -496,6 +529,9 @@

 void nsRetrievalContextWayland::SetPrimaryDataOffer(

     zwp_primary_selection_offer_v1* aPrimaryDataOffer) {

+  LOGCLIP(("nsRetrievalContextWayland::SetPrimaryDataOffer (primary ZWP)%p\n",

+           aPrimaryDataOffer));

+

   // Release any primary offer we have.

   mPrimaryOffer = nullptr;

@@ -504,7 +540,11 @@

   if (aPrimaryDataOffer) {

     DataOffer* dataOffer = static_cast<DataOffer*>(

         g_hash_table_lookup(mActiveOffers, aPrimaryDataOffer));

-    NS_ASSERTION(dataOffer, "We're missing primary data offer!");

+#ifdef MOZ_LOGGING

+    if (!dataOffer) {

+      LOGCLIP(("    We're missing stored primary data offer!\n"));

+    }

+#endif

     if (dataOffer) {

       g_hash_table_remove(mActiveOffers, aPrimaryDataOffer);

       mPrimaryOffer = WrapUnique(dataOffer);

@@ -514,12 +554,19 @@

 void nsRetrievalContextWayland::AddDragAndDropDataOffer(

     wl_data_offer* aDropDataOffer) {

+  LOGCLIP(("nsRetrievalContextWayland::AddDragAndDropDataOffer %p\n",

+           aDropDataOffer));

+

   // Remove any existing D&D contexts.

   mDragContext = nullptr;

   WaylandDataOffer* dataOffer = static_cast<WaylandDataOffer*>(

       g_hash_table_lookup(mActiveOffers, aDropDataOffer));

-  NS_ASSERTION(dataOffer, "We're missing drag and drop data offer!");

+#ifdef MOZ_LOGGING

+  if (!dataOffer) {

+    LOGCLIP(("    We're missing stored Drag & Drop data offer!\n"));

+  }

+#endif

   if (dataOffer) {

     g_hash_table_remove(mActiveOffers, aDropDataOffer);

     mDragContext = new nsWaylandDragContext(dataOffer, mDisplay->GetDisplay());

@@ -531,6 +578,7 @@

 }

 void nsRetrievalContextWayland::ClearDragAndDropDataOffer(void) {

+  LOGCLIP(("nsRetrievalContextWayland::ClearDragAndDropDataOffer()\n"));

   mDragContext = nullptr;

 }

@@ -539,7 +587,7 @@

 static void data_device_data_offer(void* data,

                                    struct wl_data_device* data_device,

                                    struct wl_data_offer* offer) {

-  LOGCLIP(("data_device_data_offer() callback\n"));

+  LOGCLIP(("data_device_data_offer(), wl_data_offer %p\n", offer));

   nsRetrievalContextWayland* context =

       static_cast<nsRetrievalContextWayland*>(data);

   context->RegisterNewDataOffer(offer);

@@ -549,7 +597,7 @@

 static void data_device_selection(void* data,

                                   struct wl_data_device* wl_data_device,

                                   struct wl_data_offer* offer) {

-  LOGCLIP(("data_device_selection() callback\n"));

+  LOGCLIP(("data_device_selection(), set wl_data_offer %p\n", offer));

   nsRetrievalContextWayland* context =

       static_cast<nsRetrievalContextWayland*>(data);

   context->SetClipboardDataOffer(offer);

@@ -650,7 +698,7 @@

 static void primary_selection_data_offer(

     void* data, struct gtk_primary_selection_device* primary_selection_device,

     struct gtk_primary_selection_offer* primary_offer) {

-  LOGCLIP(("primary_selection_data_offer() callback\n"));

+  LOGCLIP(("primary_selection_data_offer()\n"));

   // create and add listener

   nsRetrievalContextWayland* context =

       static_cast<nsRetrievalContextWayland*>(data);

@@ -661,7 +709,7 @@

     void* data,

     struct zwp_primary_selection_device_v1* primary_selection_device,

     struct zwp_primary_selection_offer_v1* primary_offer) {

-  LOGCLIP(("primary_selection_data_offer() callback\n"));

+  LOGCLIP(("primary_selection_data_offer()\n"));

   // create and add listener

   nsRetrievalContextWayland* context =

       static_cast<nsRetrievalContextWayland*>(data);

@@ -671,7 +719,7 @@

 static void primary_selection_selection(

     void* data, struct gtk_primary_selection_device* primary_selection_device,

     struct gtk_primary_selection_offer* primary_offer) {

-  LOGCLIP(("primary_selection_selection() callback\n"));

+  LOGCLIP(("primary_selection_selection()\n"));

   nsRetrievalContextWayland* context =

       static_cast<nsRetrievalContextWayland*>(data);

   context->SetPrimaryDataOffer(primary_offer);

@@ -681,7 +729,7 @@

     void* data,

     struct zwp_primary_selection_device_v1* primary_selection_device,

     struct zwp_primary_selection_offer_v1* primary_offer) {

-  LOGCLIP(("primary_selection_selection() callback\n"));

+  LOGCLIP(("primary_selection_selection()\n"));

   nsRetrievalContextWayland* context =

       static_cast<nsRetrievalContextWayland*>(data);

   context->SetPrimaryDataOffer(primary_offer);

@@ -803,17 +851,26 @@

 void nsRetrievalContextWayland::TransferFastTrackClipboard(

     int aClipboardRequestNumber, GtkSelectionData* aSelectionData) {

+  LOGCLIP(("nsRetrievalContextWayland::TransferFastTrackClipboard()\n"));

+

   if (mClipboardRequestNumber == aClipboardRequestNumber) {

+    LOGCLIP(("    request number matches\n"));

     int dataLength = gtk_selection_data_get_length(aSelectionData);

-    if (dataLength > 0) {

-      mClipboardDataLength = dataLength;

-      mClipboardData = reinterpret_cast<char*>(

-          g_malloc(sizeof(char) * (mClipboardDataLength + 1)));

-      memcpy(mClipboardData, gtk_selection_data_get_data(aSelectionData),

-             sizeof(char) * mClipboardDataLength);

-      mClipboardData[mClipboardDataLength] = '\0';

+    if (!dataLength) {

+      LOGCLIP(

+          ("    gtk_selection_data_get_length() returned 0 data length!\n"));

+      return;

     }

+    LOGCLIP(("    fastracking %d bytes of data.\n", dataLength));

+    mClipboardDataLength = dataLength;

+    mClipboardData = reinterpret_cast<char*>(

+        g_malloc(sizeof(char) * (mClipboardDataLength + 1)));

+    memcpy(mClipboardData, gtk_selection_data_get_data(aSelectionData),

+           sizeof(char) * mClipboardDataLength);

+    mClipboardData[mClipboardDataLength] = '\0';

+    LOGCLIP(("    done, mClipboardData = %p\n", mClipboardData));

   } else {

+    LOGCLIP(("    request number does not match!\n"));

     NS_WARNING("Received obsoleted clipboard data!");

   }

 }

@@ -833,25 +890,29 @@

    */

   GdkAtom selection = GetSelectionAtom(aWhichClipboard);

   if (gdk_selection_owner_get(selection)) {

-    LOGCLIP(("  Internal clipboard content\n"));

+    LOGCLIP(("  Asking for internal clipboard content.\n"));

     mClipboardRequestNumber++;

     gtk_clipboard_request_contents(

         gtk_clipboard_get(selection), gdk_atom_intern(aMimeType, FALSE),

         wayland_clipboard_contents_received,

         new FastTrackClipboard(mClipboardRequestNumber, this));

   } else {

-    LOGCLIP(("  Remote clipboard content\n"));

+    LOGCLIP(("  Asking for remote clipboard content.\n"));

     const auto& dataOffer =

         (selection == GDK_SELECTION_PRIMARY) ? mPrimaryOffer : mClipboardOffer;

     if (!dataOffer) {

       // Something went wrong. We're requested to provide clipboard data

       // but we haven't got any from wayland.

-      NS_WARNING("Requested data without valid DataOffer!");

+      LOGCLIP(("  We're missing dataOffer! mClipboardData = null\n"));

       mClipboardData = nullptr;

       mClipboardDataLength = 0;

     } else {

+      LOGCLIP(

+          ("  Getting clipboard data from compositor, MIME %s\n", aMimeType));

       mClipboardData = dataOffer->GetData(mDisplay->GetDisplay(), aMimeType,

                                           &mClipboardDataLength);

+      LOGCLIP(("  Got %d bytes of data, mClipboardData = %p\n",

+               mClipboardDataLength, mClipboardData));

     }

   }

@@ -861,25 +922,36 @@

 const char* nsRetrievalContextWayland::GetClipboardText(

     int32_t aWhichClipboard) {

-  LOGCLIP(("nsRetrievalContextWayland::GetClipboardText [%p]\n", this));

+  GdkAtom selection = GetSelectionAtom(aWhichClipboard);

-  GdkAtom selection = GetSelectionAtom(aWhichClipboard);

+  LOGCLIP(("nsRetrievalContextWayland::GetClipboardText [%p], clipboard %s\n",

+           this,

+           (selection == GDK_SELECTION_PRIMARY) ? "Primary" : "Selection"));

+

   const auto& dataOffer =

       (selection == GDK_SELECTION_PRIMARY) ? mPrimaryOffer : mClipboardOffer;

-  if (!dataOffer) return nullptr;

+  if (!dataOffer) {

+    LOGCLIP(("  We're missing data offer!\n"));

+    return nullptr;

+  }

   for (unsigned int i = 0; i < TEXT_MIME_TYPES_NUM; i++) {

     if (dataOffer->HasTarget(sTextMimeTypes[i])) {

+      LOGCLIP(("  We have %s MIME type in clipboard, ask for it.\n",

+               sTextMimeTypes[i]));

       uint32_t unused;

       return GetClipboardData(sTextMimeTypes[i], aWhichClipboard, &unused);

     }

   }

+

+  LOGCLIP(("  There isn't text MIME type in clipboard!\n"));

   return nullptr;

 }

 void nsRetrievalContextWayland::ReleaseClipboardData(

     const char* aClipboardData) {

-  LOGCLIP(("nsRetrievalContextWayland::ReleaseClipboardData [%p]\n", this));

+  LOGCLIP(("nsRetrievalContextWayland::ReleaseClipboardData [%p]\n",

+           aClipboardData));

   NS_ASSERTION(aClipboardData == mClipboardData,

                "Releasing unknown clipboard data!");