Set encoding to UTF-8 for HTML Imports if no encoding is specified in the HTTP response

Source/core/html/imports/HTMLImportLoader.cpp

Index: Source/core/html/imports/HTMLImportLoader.cpp
diff --git a/Source/core/html/imports/HTMLImportLoader.cpp b/Source/core/html/imports/HTMLImportLoader.cpp
index 8dbd88dcd486969bcd4f82b164731bb2ec09f8b7..0459452e604c909c3bf1c9a3a4df68c38fe18d24 100644
--- a/Source/core/html/imports/HTMLImportLoader.cpp
+++ b/Source/core/html/imports/HTMLImportLoader.cpp
@@ -108,7 +108,7 @@ HTMLImportLoader::State HTMLImportLoader::startWritingAndParsing(const ResourceR
     DocumentInit init = DocumentInit(response.url(), 0, m_controller->master()->contextDocument(), m_controller)
         .withRegistrationContext(m_controller->master()->registrationContext());
     m_importedDocument = HTMLDocument::create(init);
-    m_writer = DocumentWriter::create(m_importedDocument.get(), response.mimeType(), response.textEncodingName());
+    m_writer = DocumentWriter::create(m_importedDocument.get(), response.mimeType(), "UTF-8");
 
     return StateLoading;
 }