[Blob] BlobReader class & tests, and removal of all redundant reading.

net/base/upload_element_reader.cc

Index: net/base/upload_element_reader.cc
diff --git a/net/base/upload_element_reader.cc b/net/base/upload_element_reader.cc
index 70b657cf868bf9dec74c4d342f218bf12a3929a2..2a95eb816aec97f64924c265879cb67bb53e11c0 100644
--- a/net/base/upload_element_reader.cc
+++ b/net/base/upload_element_reader.cc
@@ -6,11 +6,6 @@
 
 namespace net {
 
-const UploadDiskCacheEntryElementReader*
-UploadElementReader::AsDiskCacheEntryReaderForTests() const {
-  return nullptr;
-}
-
 const UploadBytesElementReader* UploadElementReader::AsBytesReader() const {
   return nullptr;
 }