Remove unnecessary includes in src/pdf/

src/pdf/SkPDFMetadata.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPDFMetadata_DEFINED
 #define SkPDFMetadata_DEFINED
 
 #include "SkDocument.h"
-#include "SkTime.h"
 
 class SkPDFObject;
 
 namespace SkPDFMetadata {
 sk_sp<SkPDFObject> MakeDocumentInformationDict(const SkDocument::PDFMetadata&);
 
 struct UUID {
     uint8_t fData[16];
 };
 
 UUID CreateUUID(const SkDocument::PDFMetadata&);
 
 sk_sp<SkPDFObject> MakePdfId(const UUID& doc, const UUID& instance);
 
 sk_sp<SkPDFObject> MakeXMPObject(const SkDocument::PDFMetadata&,
                                  const UUID& doc,
                                  const UUID& instance);
 
 #ifdef SK_SUPPORT_LEGACY_DOCUMENT_API
 void SetMetadataByKey(const SkString& key,
                       const SkString& value,
                       SkDocument::PDFMetadata*);
 #endif
 }
 #endif  // SkPDFMetadata_DEFINED