[FileSystem] Remove GetByteSize() from FileSpec

This patch removes the GetByteSize method from FileSpec and updates its
uses with calls to the FileSystem.

Differential revision: https://reviews.llvm.org/D53788

llvm-svn: 345812
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index 0dcf668..2a2448c 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -1648,7 +1648,8 @@
   lldb::offset_t dwo_file_data_offset = 0;
   ObjectFileSP dwo_obj_file = ObjectFile::FindPlugin(
       GetObjectFile()->GetModule(), &dwo_file, file_offset,
-      dwo_file.GetByteSize(), dwo_file_data_sp, dwo_file_data_offset);
+      FileSystem::Instance().GetByteSize(dwo_file), dwo_file_data_sp,
+      dwo_file_data_offset);
   if (dwo_obj_file == nullptr)
     return nullptr;