Make classes and structures in core/dom fast-allocated.

Source/core/dom/DocumentEncodingData.h

Index: Source/core/dom/DocumentEncodingData.h
diff --git a/Source/core/dom/DocumentEncodingData.h b/Source/core/dom/DocumentEncodingData.h
index 1bc2fec00392fcbda1616ec56d28515a24882d20..da2342bb6349e7d3e64f8ad25905f7008471a0ec 100644
--- a/Source/core/dom/DocumentEncodingData.h
+++ b/Source/core/dom/DocumentEncodingData.h
@@ -32,12 +32,14 @@
 #define DocumentEncodingData_h
 
 #include "platform/CrossThreadCopier.h"
+#include "wtf/Allocator.h"
 #include "wtf/text/TextEncoding.h"
 
 namespace blink {
 class TextResourceDecoder;
 
 class DocumentEncodingData {
+    DISALLOW_ALLOCATION();
 public:
     DocumentEncodingData();
     explicit DocumentEncodingData(const TextResourceDecoder&);