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

Source/core/fetch/FontResource.cpp

Index: Source/core/fetch/FontResource.cpp
diff --git a/Source/core/fetch/FontResource.cpp b/Source/core/fetch/FontResource.cpp
old mode 100644
new mode 100755
index 0fdbcc1d39e9a76f602f07f8dc2a14315522a5f4..0f026d07800376ce866535e412d485aaf5396dd3
--- a/Source/core/fetch/FontResource.cpp
+++ b/Source/core/fetch/FontResource.cpp
@@ -111,7 +111,7 @@ bool FontResource::ensureSVGFontData()
 
             OwnPtr<TextResourceDecoder> decoder = TextResourceDecoder::create("application/xml");
             String svgSource = decoder->decode(m_data->data(), m_data->size());
-            svgSource.append(decoder->flush());
+            svgSource = svgSource + decoder->flush();
 
             m_externalSVGDocument->setContent(svgSource);