pdfviewer: pass the page number, report failure if at least one render fails, and check that xref s…

experimental/PdfViewer/pdfparser/native/SkNativeParsedPDF.cpp

 #include "SkNativeParsedPDF.h"
 #include "SkPdfNativeTokenizer.h"
 #include "SkPdfBasics.h"
 #include "SkPdfObject.h"
 
 #include <stdio.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 
@@ skipping 207 matching lines @@
 
 }
 
 // TODO(edisonn): NYI
 SkNativeParsedPDF::~SkNativeParsedPDF() {
     sk_free((void*)fFileContent);
     delete fAllocator;
 }
 
 const unsigned char* SkNativeParsedPDF::readCrossReferenceSection(const unsigned char* xrefStart, const unsigned char* trailerEnd) {
-    const unsigned char* current = ignoreLine(xrefStart, trailerEnd);  // TODO(edisonn): verify next keyord is "xref", use nextObject here
+    SkPdfObject xref;
+    const unsigned char* current = nextObject(0, xrefStart, trailerEnd, &xref, NULL, NULL);
+
+    if (!xref.isKeyword("xref")) {
+        return trailerEnd;
+    }
 
     SkPdfObject token;
     while (current < trailerEnd) {
         token.reset();
         const unsigned char* previous = current;
         current = nextObject(0, current, trailerEnd, &token, NULL, NULL);
         if (!token.isInteger()) {
             return previous;
         }
 
@@ skipping 312 matching lines @@
     return (SkPdfObject*)ref;
 }
 
 size_t SkNativeParsedPDF::bytesUsed() const {
     return fAllocator->bytesUsed() +
            fContentLength +
            fObjects.count() * sizeof(PublicObjectEntry) +
            fPages.count() * sizeof(SkPdfPageObjectDictionary*) +
            sizeof(*this);
 }