Remove 'String::append' from some of the blink source.

Source/core/fetch/XSLStyleSheetResource.cpp

Index: Source/core/fetch/XSLStyleSheetResource.cpp
diff --git a/Source/core/fetch/XSLStyleSheetResource.cpp b/Source/core/fetch/XSLStyleSheetResource.cpp
old mode 100644
new mode 100755
index 053a445d456640d44516c275622671d2a230703c..d203585eb6afb140a19d1ba2849cacc6b601a2e3
--- a/Source/core/fetch/XSLStyleSheetResource.cpp
+++ b/Source/core/fetch/XSLStyleSheetResource.cpp
@@ -68,10 +68,8 @@ String XSLStyleSheetResource::encoding() const
 
 void XSLStyleSheetResource::checkNotify()
 {
-    if (m_data.get()) {
-        m_sheet = m_decoder->decode(m_data->data(), encodedSize());
-        m_sheet.append(m_decoder->flush());
-    }
+    if (m_data.get())
+        m_sheet = m_decoder->decode(m_data->data(), encodedSize()) + m_decoder->flush();
 
     ResourceClientWalker<StyleSheetResourceClient> w(m_clients);
     while (StyleSheetResourceClient* c = w.next())