net: Make UploadData::GetContentLength() asynchronous.

net/base/upload_data_stream.cc

Index: net/base/upload_data_stream.cc
diff --git a/net/base/upload_data_stream.cc b/net/base/upload_data_stream.cc
index 550a117e90a253927c304a28b658c36b1f0b9ebc..181b3f7ba9bcf27c9b60dce5afbdb45fb00955ed 100644
--- a/net/base/upload_data_stream.cc
+++ b/net/base/upload_data_stream.cc
@@ -22,7 +22,7 @@ UploadDataStream::~UploadDataStream() {
 int UploadDataStream::Init() {
   DCHECK(!initialized_successfully_);
 
-  total_size_ = upload_data_->GetContentLength();
+  total_size_ = upload_data_->GetContentLengthSyncHack();
   const int result = FillBuffer();
   initialized_successfully_ = (result == OK);
   return result;
@@ -114,6 +114,8 @@ int UploadDataStream::FillBuffer() {
           }
         }
         element_file_bytes_remaining_ = element.GetContentLength();
+        // Temporarily allow until fix: http://crbug.com/72001.
+        base::ThreadRestrictions::ScopedAllowIO allow_io;
         element_file_stream_.reset(element.NewFileStreamForReading());
       }