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

Source/core/fetch/CSSStyleSheetResource.cpp

Index: Source/core/fetch/CSSStyleSheetResource.cpp
diff --git a/Source/core/fetch/CSSStyleSheetResource.cpp b/Source/core/fetch/CSSStyleSheetResource.cpp
old mode 100644
new mode 100755
index 7952ec5da2ec71af331f574e7073183978add410..5edeabcbb866fc19cd35ded889ce093e562b0084
--- a/Source/core/fetch/CSSStyleSheetResource.cpp
+++ b/Source/core/fetch/CSSStyleSheetResource.cpp
@@ -89,7 +89,7 @@ const String CSSStyleSheetResource::sheetText(bool enforceMIMEType, bool* hasVal
 
     // Don't cache the decoded text, regenerating is cheap and it can use quite a bit of memory
     String sheetText = m_decoder->decode(m_data->data(), m_data->size());
-    sheetText.append(m_decoder->flush());
+    sheetText = sheetText + m_decoder->flush();
     return sheetText;
 }