diff --git a/dom/base/StructuredCloneHelper.cpp b/dom/base/StructuredCloneHelper.cpp
index 7975e42e1bd..baad651b0a0 100644
--- a/dom/base/StructuredCloneHelper.cpp
+++ b/dom/base/StructuredCloneHelper.cpp
@@ -21,6 +21,8 @@
 #include "mozilla/dom/StructuredClone.h"
 #include "mozilla/dom/MessagePort.h"
 #include "mozilla/dom/MessagePortBinding.h"
+#include "mozilla/dom/OffscreenCanvas.h"
+#include "mozilla/dom/OffscreenCanvasBinding.h"
 #include "mozilla/dom/PMessagePort.h"
 #include "mozilla/dom/StructuredCloneTags.h"
 #include "mozilla/dom/SubtleCryptoBinding.h"
@@ -1062,6 +1064,25 @@ StructuredCloneHelper::ReadTransferCallback(JSContext* aCx,
     return true;
   }
 
+  if (aTag == SCTAG_DOM_CANVAS) {
+    MOZ_ASSERT(mContext == SameProcessSameThread ||
+               mContext == SameProcessDifferentThread);
+    MOZ_ASSERT(aContent);
+    OffscreenCanvasCloneData* data =
+      static_cast<OffscreenCanvasCloneData*>(aContent);
+    nsRefPtr<OffscreenCanvas> canvas = OffscreenCanvas::CreateFromCloneData(data);
+    delete data;
+
+    JS::Rooted<JS::Value> value(aCx);
+    if (!GetOrCreateDOMReflector(aCx, canvas, &value)) {
+      JS_ClearPendingException(aCx);
+      return false;
+    }
+
+    aReturnObject.set(&value.toObject());
+    return true;
+  }
+
   return false;
 }
 
@@ -1093,6 +1114,24 @@ StructuredCloneHelper::WriteTransferCallback(JSContext* aCx,
 
       return true;
     }
+
+    if (mContext == SameProcessSameThread ||
+        mContext == SameProcessDifferentThread) {
+      OffscreenCanvas* canvas = nullptr;
+      rv = UNWRAP_OBJECT(OffscreenCanvas, aObj, canvas);
+      if (NS_SUCCEEDED(rv)) {
+        MOZ_ASSERT(canvas);
+
+        *aExtraData = 0;
+        *aTag = SCTAG_DOM_CANVAS;
+        *aOwnership = JS::SCTAG_TMO_CUSTOM;
+        *aContent = canvas->ToCloneData();
+        MOZ_ASSERT(*aContent);
+        canvas->SetNeutered();
+
+        return true;
+      }
+    }
   }
 
   return false;
@@ -1110,6 +1149,17 @@ StructuredCloneHelper::FreeTransferCallback(uint32_t aTag,
     MOZ_ASSERT(!aContent);
     MOZ_ASSERT(aExtraData < mPortIdentifiers.Length());
     MessagePort::ForceClose(mPortIdentifiers[aExtraData]);
+    return;
+  }
+
+  if (aTag == SCTAG_DOM_CANVAS) {
+    MOZ_ASSERT(mContext == SameProcessSameThread ||
+               mContext == SameProcessDifferentThread);
+    MOZ_ASSERT(aContent);
+    OffscreenCanvasCloneData* data =
+      static_cast<OffscreenCanvasCloneData*>(aContent);
+    delete data;
+    return;
   }
 }
 
diff --git a/dom/base/StructuredCloneTags.h b/dom/base/StructuredCloneTags.h
index fe6ccdf371f..f1fec533d4d 100644
--- a/dom/base/StructuredCloneTags.h
+++ b/dom/base/StructuredCloneTags.h
@@ -48,6 +48,9 @@ enum StructuredCloneTags {
 
   SCTAG_DOM_FORMDATA,
 
+  // This tag is for OffscreenCanvas.
+  SCTAG_DOM_CANVAS,
+
   SCTAG_DOM_MAX
 };
 
diff --git a/js/public/StructuredClone.h b/js/public/StructuredClone.h
index e95b4ef8345..fb72fb3ed6c 100644
--- a/js/public/StructuredClone.h
+++ b/js/public/StructuredClone.h
@@ -195,17 +195,20 @@ class JS_PUBLIC_API(JSAutoStructuredCloneBuffer) {
     void clear(const JSStructuredCloneCallbacks* optionalCallbacks=nullptr, void* closure=nullptr);
 
     // Copy some memory. It will be automatically freed by the destructor.
-    bool copy(const uint64_t* data, size_t nbytes, uint32_t version=JS_STRUCTURED_CLONE_VERSION);
+    bool copy(const uint64_t* data, size_t nbytes, uint32_t version=JS_STRUCTURED_CLONE_VERSION,
+              const JSStructuredCloneCallbacks* callbacks=nullptr, void* closure=nullptr);
 
     // Adopt some memory. It will be automatically freed by the destructor.
     // data must have been allocated by the JS engine (e.g., extracted via
     // JSAutoStructuredCloneBuffer::steal).
-    void adopt(uint64_t* data, size_t nbytes, uint32_t version=JS_STRUCTURED_CLONE_VERSION);
+    void adopt(uint64_t* data, size_t nbytes, uint32_t version=JS_STRUCTURED_CLONE_VERSION,
+               const JSStructuredCloneCallbacks* callbacks=nullptr, void* closure=nullptr);
 
     // Release the buffer and transfer ownership to the caller. The caller is
     // responsible for calling JS_ClearStructuredClone or feeding the memory
     // back to JSAutoStructuredCloneBuffer::adopt.
-    void steal(uint64_t** datap, size_t* nbytesp, uint32_t* versionp=nullptr);
+    void steal(uint64_t** datap, size_t* nbytesp, uint32_t* versionp=nullptr,
+               const JSStructuredCloneCallbacks** callbacks=nullptr, void** closure=nullptr);
 
     // Abandon ownership of any transferable objects stored in the buffer,
     // without freeing the buffer itself. Useful when copying the data out into
diff --git a/js/src/vm/StructuredClone.cpp b/js/src/vm/StructuredClone.cpp
index 00c916eb73d..505b3198e6c 100644
--- a/js/src/vm/StructuredClone.cpp
+++ b/js/src/vm/StructuredClone.cpp
@@ -2054,7 +2054,7 @@ JS_StructuredClone(JSContext* cx, HandleValue value, MutableHandleValue vp,
 JSAutoStructuredCloneBuffer::JSAutoStructuredCloneBuffer(JSAutoStructuredCloneBuffer&& other)
 {
     ownTransferables_ = other.ownTransferables_;
-    other.steal(&data_, &nbytes_, &version_);
+    other.steal(&data_, &nbytes_, &version_, &callbacks_, &closure_);
 }
 
 JSAutoStructuredCloneBuffer&
@@ -2063,7 +2063,7 @@ JSAutoStructuredCloneBuffer::operator=(JSAutoStructuredCloneBuffer&& other)
     MOZ_ASSERT(&other != this);
     clear();
     ownTransferables_ = other.ownTransferables_;
-    other.steal(&data_, &nbytes_, &version_);
+    other.steal(&data_, &nbytes_, &version_, &callbacks_, &closure_);
     return *this;
 }
 
@@ -2088,7 +2088,9 @@ JSAutoStructuredCloneBuffer::clear(const JSStructuredCloneCallbacks* optionalCal
 }
 
 bool
-JSAutoStructuredCloneBuffer::copy(const uint64_t* srcData, size_t nbytes, uint32_t version)
+JSAutoStructuredCloneBuffer::copy(const uint64_t* srcData, size_t nbytes, uint32_t version,
+                                  const JSStructuredCloneCallbacks* callbacks,
+                                  void* closure)
 {
     // transferable objects cannot be copied
     if (StructuredCloneHasTransferObjects(data_, nbytes_))
@@ -2104,31 +2106,45 @@ JSAutoStructuredCloneBuffer::copy(const uint64_t* srcData, size_t nbytes, uint32
     data_ = newData;
     nbytes_ = nbytes;
     version_ = version;
+    callbacks_ = callbacks;
+    closure_ = closure;
     ownTransferables_ = NoTransferables;
     return true;
 }
 
 void
-JSAutoStructuredCloneBuffer::adopt(uint64_t* data, size_t nbytes, uint32_t version)
+JSAutoStructuredCloneBuffer::adopt(uint64_t* data, size_t nbytes, uint32_t version,
+                                   const JSStructuredCloneCallbacks* callbacks,
+                                   void* closure)
 {
     clear();
     data_ = data;
     nbytes_ = nbytes;
     version_ = version;
+    callbacks_ = callbacks;
+    closure_ = closure;
     ownTransferables_ = OwnsTransferablesIfAny;
 }
 
 void
-JSAutoStructuredCloneBuffer::steal(uint64_t** datap, size_t* nbytesp, uint32_t* versionp)
+JSAutoStructuredCloneBuffer::steal(uint64_t** datap, size_t* nbytesp, uint32_t* versionp,
+                                   const JSStructuredCloneCallbacks** callbacks,
+                                   void** closure)
 {
     *datap = data_;
     *nbytesp = nbytes_;
     if (versionp)
         *versionp = version_;
+    if (callbacks)
+        *callbacks = callbacks_;
+    if (closure)
+        *closure = closure_;
 
     data_ = nullptr;
     nbytes_ = 0;
     version_ = 0;
+    callbacks_ = 0;
+    closure_ = 0;
     ownTransferables_ = NoTransferables;
 }