Bug 1559403 - Implement nsIStringInputStream.setUTF8Data. r=froydnj

Differential Revision: https://phabricator.services.mozilla.com/D35027

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

xpcom/io/nsIStringStream.idl

@@ -36,6 +36,16 @@ interface nsIStringInputStream : nsIInputStream
      */
     void setData(in string data, in long dataLen);
 
+    /**
+     * SetUTF8Data - encode input data to UTF-8 and assign it to the input
+     * stream.
+     *
+     * @param data    - stream data
+     *
+     * NOTE: This method is meant to be used by JS callers,
+     */
+    void setUTF8Data(in AUTF8String data);
+
     /**
      * NOTE: the following methods are designed to give C++ code added control
      * over the ownership and lifetime of the stream data.  Use with care :-)

xpcom/io/nsStringStream.cpp

@@ -193,6 +193,11 @@ nsStringInputStream::SetData(const char* aData, int32_t aDataLen) {
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsStringInputStream::SetUTF8Data(const nsACString& aData) {
+  return nsStringInputStream::SetData(aData);
+}
+
 NS_IMETHODIMP
 nsStringInputStream::AdoptData(char* aData, int32_t aDataLen) {
   ReentrantMonitorAutoEnter lock(mMon);