Update Linux to use scoped_refptr<T>::get() rather than implicit "operator T*"

net/disk_cache/block_files.cc

Index: net/disk_cache/block_files.cc
diff --git a/net/disk_cache/block_files.cc b/net/disk_cache/block_files.cc
index 0b5bf824580110ac7cf22d4f3bd750c0c660d449..873221255c336755913e49491a2112f5cdbdaa49 100644
--- a/net/disk_cache/block_files.cc
+++ b/net/disk_cache/block_files.cc
@@ -450,7 +450,7 @@ bool BlockFiles::OpenBlockFile(int index) {
     return false;
   }
 
-  BlockHeader header(file);
+  BlockHeader header(file.get());
   if (kBlockMagic != header->magic || kBlockVersion2 != header->version) {
     LOG(ERROR) << "Invalid file version or magic " << name.value();
     return false;