refactoring for pdf viewer lib

experimental/PdfViewer/SkPdfUtils.cpp

+#include "SkPdfUtils.h"
+
+bool ArrayFromDictionary(const PdfMemDocument* pdfDoc,
+                         const PdfDictionary& dict,
+                         const char* key,
+                         const char* abr,
+                         SkPdfArray* data) {return false;}
+
+bool FileSpecFromDictionary(const PdfMemDocument* pdfDoc,
+                         const PdfDictionary& dict,
+                         const char* key,
+                         const char* abr,
+                         SkPdfFileSpec* data) {return false;}
+
+bool StreamFromDictionary(const PdfMemDocument* pdfDoc,
+                         const PdfDictionary& dict,
+                         const char* key,
+                         const char* abr,
+                         SkPdfStream** data);
+
+bool TreeFromDictionary(const PdfMemDocument* pdfDoc,
+                         const PdfDictionary& dict,
+                         const char* key,
+                         const char* abr,
+                         SkPdfTree** data) {return false;}
+
+bool DateFromDictionary(const PdfMemDocument* pdfDoc,
+                         const PdfDictionary& dict,
+                         const char* key,
+                         const char* abr,
+                         SkPdfDate* data) {return false;}
+
+bool FunctionFromDictionary(const PdfMemDocument* pdfDoc,
+                         const PdfDictionary& dict,
+                         const char* key,
+                         const char* abr,
+                         SkPdfFunction* data) {return false;}