pdf viewer: fix a few warnings, and enable warning as errors

experimental/PdfViewer/pdfparser/native/SkPdfNativeTokenizer.cpp

 
 #include "SkPdfNativeTokenizer.h"
 #include "SkPdfObject.h"
 #include "SkPdfConfig.h"
 
 #include "SkPdfStreamCommonDictionary_autogen.h"
 
 unsigned char* skipPdfWhiteSpaces(unsigned char* start, unsigned char* end) {
     while (start < end && isPdfWhiteSpace(*start)) {
         if (*start == kComment_PdfDelimiter) {
@@ skipping 682 matching lines @@
 SkPdfNativeTokenizer::SkPdfNativeTokenizer(unsigned char* buffer, int len, const SkPdfMapper* mapper, SkPdfAllocator* allocator) : fMapper(mapper), fAllocator(allocator), fEmpty(false), fHasPutBack(false) {
     fUncompressedStreamStart = fUncompressedStream = (unsigned char*)fAllocator->alloc(len);
     fUncompressedStreamEnd = fUncompressedStream + len;
     memcpy(fUncompressedStream, buffer, len);
 }
 
 SkPdfNativeTokenizer::~SkPdfNativeTokenizer() {
     // free the unparsed stream, we don't need it.
     // the parsed one is locked as it contains the strings and keywords referenced in objects
     if (fUncompressedStream) {
-        realloc(fUncompressedStreamStart, fUncompressedStream - fUncompressedStreamStart);
+        void* dummy = realloc(fUncompressedStreamStart, fUncompressedStream - fUncompressedStreamStart);
+        SkASSERT(dummy == fUncompressedStreamStart);
+        fUncompressedStreamStart = (unsigned char*)dummy;  // suporess compiler warning
     } else {
         SkASSERT(false);
     }
 }
 
 bool SkPdfNativeTokenizer::readTokenCore(PdfToken* token) {
     token->fKeyword = NULL;
     token->fObject = NULL;
 
     fUncompressedStream = skipPdfWhiteSpaces(fUncompressedStream, fUncompressedStreamEnd);
@@ skipping 49 matching lines @@
 
     if (fEmpty) {
 #ifdef PDF_TRACE
     printf("EMPTY TOKENIZER\n");
 #endif
         return false;
     }
 
     return readTokenCore(token);
 }