pdfviewer: add indexed rbg image support, enhanche caching(setData) for SkPdfObject

experimental/PdfViewer/pdfparser/native/SkNativeParsedPDF.h

 #ifndef EXPERIMENTAL_PDFVIEWER_PDFPARSER_NATIVE_SKNATIVEPARSEDPDF_H_
 #define EXPERIMENTAL_PDFVIEWER_PDFPARSER_NATIVE_SKNATIVEPARSEDPDF_H_
 
 #include "SkRect.h"
 #include "SkTDArray.h"
 
 class SkCanvas;
 
 class SkPdfAllocator;
 class SkPdfMapper;
@@ skipping 46 matching lines @@
     SkPdfPageObjectDictionary* page(int page);
 
     const SkPdfMapper* mapper() const;
     SkPdfAllocator* allocator() const;
 
     SkPdfReal* createReal(double value) const;
     SkPdfInteger* createInteger(int value) const;
     // the string does not own the char*
     SkPdfString* createString(const unsigned char* sz, size_t len) const;
 
-    SkPdfObject* resolveReference(const SkPdfObject* ref);
+    SkPdfObject* resolveReference(SkPdfObject* ref);
 
     // Reports an approximation of all the memory usage.
     size_t bytesUsed() const;
 
 private:
 
     // Takes ownership of bytes.
     void init(const void* bytes, size_t length);
     void loadWithoutXRef();
 
@@ skipping 10 matching lines @@
 
     SkPdfObject* readObject(int id/*, int generation*/);
 
     void fillPages(SkPdfPageTreeNodeDictionary* tree);
 
     // private fields
     SkPdfAllocator* fAllocator;
     SkPdfMapper* fMapper;
     const unsigned char* fFileContent;
     size_t fContentLength;
-    const SkPdfObject* fRootCatalogRef;
+    SkPdfObject* fRootCatalogRef;
     SkPdfCatalogDictionary* fRootCatalog;
 
     mutable SkTDArray<PublicObjectEntry> fObjects;
     SkTDArray<SkPdfPageObjectDictionary*> fPages;
 };
 
 #endif  // EXPERIMENTAL_PDFVIEWER_PDFPARSER_NATIVE_SKNATIVEPARSEDPDF_H_