Remove cross_thread_copier.h from document_encoding_data.h.

DocumentEncodingData is never passed across threads.

Bug: 242216, 689702
Change-Id: If5a78abdb39399c3283480310f5bbe1fab669700
Reviewed-on: https://chromium-review.googlesource.com/1131046
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573694}

third_party/blink/renderer/core/dom/document_encoding_data.h

@@ -31,7 +31,6 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_DOM_DOCUMENT_ENCODING_DATA_H_
 #define THIRD_PARTY_BLINK_RENDERER_CORE_DOM_DOCUMENT_ENCODING_DATA_H_
 
-#include "third_party/blink/renderer/platform/cross_thread_copier.h"
 #include "third_party/blink/renderer/platform/wtf/allocator.h"
 #include "third_party/blink/renderer/platform/wtf/text/text_encoding.h"
 
@@ -56,10 +55,6 @@ class DocumentEncodingData {
   bool saw_decoding_error_;
 };
 
-template <>
-struct CrossThreadCopier<DocumentEncodingData>
-    : public CrossThreadCopierPassThrough<DocumentEncodingData> {};
-
 inline bool operator!=(const DocumentEncodingData& a,
                        const DocumentEncodingData& b) {
   return a.Encoding() != b.Encoding() ||