PDF: Use a vector instead of a list in DocumentLoader.

pdf/document_loader.h

Index: pdf/document_loader.h
diff --git a/pdf/document_loader.h b/pdf/document_loader.h
index c9d355b99ad1c15555b3aa4c0cf613658bae46da..af39390e975f657821a45bf4321d112e62294d31 100644
--- a/pdf/document_loader.h
+++ b/pdf/document_loader.h
@@ -128,7 +128,7 @@ class DocumentLoader {
   bool is_multipart_;
   std::string multipart_boundary_;
   uint32_t requests_count_;
-  std::list<std::vector<unsigned char> > chunk_buffer_;
+  std::vector<std::vector<unsigned char> > chunk_buffer_;
 };
 
 }  // namespace chrome_pdf