Bug 1225219 Implement ErrorResult::CloneTo(). r=bz

dom/bindings/BindingUtils.cpp

@@ -466,6 +466,36 @@ ErrorResult::operator=(ErrorResult&& aRHS)
   return *this;
 }
 
+void
+ErrorResult::CloneTo(ErrorResult& aRv) const
+{
+  aRv.ClearUnionData();
+  aRv.mResult = mResult;
+  aRv.mMightHaveUnreportedJSException = mMightHaveUnreportedJSException;
+
+  if (IsErrorWithMessage()) {
+#ifdef DEBUG
+    aRv.mUnionState = HasMessage;
+#endif
+    aRv.mMessage = new Message();
+    aRv.mMessage->mArgs = mMessage->mArgs;
+    aRv.mMessage->mErrorNumber = mMessage->mErrorNumber;
+  } else if (IsDOMException()) {
+#ifdef DEBUG
+    aRv.mUnionState = HasDOMExceptionInfo;
+#endif
+    aRv.mDOMExceptionInfo = new DOMExceptionInfo(mDOMExceptionInfo->mRv,
+                                                 mDOMExceptionInfo->mMessage);
+  } else if (IsJSException()) {
+#ifdef DEBUG
+    aRv.mUnionState = HasJSException;
+#endif
+    JSContext* cx = nsContentUtils::RootingCxForThread();
+    JS::Rooted<JS::Value> exception(cx, mJSException);
+    aRv.ThrowJSException(cx, exception);
+  }
+}
+
 void
 ErrorResult::SuppressException()
 {

dom/bindings/ErrorResult.h

@@ -115,6 +115,11 @@ public:
     AssignErrorCode(rv);
   }
 
+  // Duplicate our current state on the given ErrorResult object.  Any existing
+  // errors or messages on the target will be suppressed before cloning.  Our
+  // own error state remains unchanged.
+  void CloneTo(ErrorResult& aRv) const;
+
   // Use SuppressException when you want to suppress any exception that might be
   // on the ErrorResult.  After this call, the ErrorResult will be back a "no
   // exception thrown" state.