pdfviewer: ignore more bad stauff in pdfs

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 85 matching lines @@
         xrefByteOffset = readTrailer(trailerStart, xrefstartKeywordLine, storeCatalog);
         storeCatalog = false;
     }
 
     // TODO(edisonn): warn/error expect fObjects[fRefCatalogId].fGeneration == fRefCatalogGeneration
     // TODO(edisonn): security, verify that SkPdfCatalogDictionary is indeed using mapper
     // load catalog
 
     if (fRootCatalogRef) {
         fRootCatalog = (SkPdfCatalogDictionary*)resolveReference(fRootCatalogRef);
-        SkPdfPageTreeNodeDictionary* tree = fRootCatalog->Pages(this);
+        if (fRootCatalog->isDictionary() && fRootCatalog->valid()) {
+            SkPdfPageTreeNodeDictionary* tree = fRootCatalog->Pages(this);
+            if (tree && tree->isDictionary() && tree->valid()) {
+                fillPages(tree);
+            }
+        }
+    }
 
-        fillPages(tree);
-    } else {
-        // TODO(edisonn): corrupted pdf, read it from beginning and rebuild (xref, trailer, or just reall all objects)
-        // 0 pages
-    }
+    // TODO(edisonn): corrupted pdf, read it from beginning and rebuild (xref, trailer, or just reall all objects)
+    // 0 pages
 
     // now actually read all objects if we want, or do it lazyly
     // and resolve references?... or not ...
 }
 
 // TODO(edisonn): NYI
 SkNativeParsedPDF::~SkNativeParsedPDF() {
     delete[] fFileContent;
     delete fAllocator;
 }
@@ skipping 283 matching lines @@
             } else {
                 fObjects[id].fResolvedReference = resolveReference(fObjects[id].fObj);
             }
         }
 
         return fObjects[id].fResolvedReference;
     }
     // TODO(edisonn): fix the mess with const, probably we need to remove it pretty much everywhere
     return (SkPdfObject*)ref;
 }