[lldb] Add comments to describe m_memory_addr and IsInMemory

[jasonmolenda]

LGTM, this isn't clear right now reading the source.

lldb/include/lldb/Symbol/ObjectFile.h

virtual size_t ReadSectionData(Section *section,
                                  size_t dst_len);
 
   // This function will transparently decompress section data if the section if
   // compressed. Note that for compressed section the resulting data size may
   // be larger than what Section::GetFileSize reports.
   virtual size_t ReadSectionData(Section *section,
                                  DataExtractor &section_data);
 
+  /// Returns true if the object file exists only in memory.
   bool IsInMemory() const { return m_memory_addr != LLDB_INVALID_ADDRESS; }
 
   // Strip linker annotations (such as @@VERSION) from symbol names.
   virtual llvm::StringRef
   StripLinkerSymbolAnnotations(llvm::StringRef symbol_name) const {
     return symbol_name;
   }
 
protected:
   lldb::addr_t m_file_offset; ///< The offset in bytes into the file, or the
                               ///address in memory
   lldb::addr_t m_length; ///< The length of this object file if it is known (can
                          ///be zero if length is unknown or can't be
                          ///determined).
   DataExtractor
       m_data; ///< The data for this object file so things can be parsed lazily.
   lldb::ProcessWP m_process_wp;
+  /// Set if the object file only exists in memory.
   const lldb::addr_t m_memory_addr;
   std::unique_ptr<lldb_private::SectionList> m_sections_up;
   std::unique_ptr<lldb_private::Symtab> m_symtab_up;
   /// We need a llvm::once_flag that we can use to avoid locking the module
   /// lock and deadlocking LLDB. See comments in ObjectFile::GetSymtab() for
   /// the full details. We also need to be able to clear the symbol table, so we
   /// need to use a std::unique_ptr to a llvm::once_flag so if we clear the
   /// symbol table, we can have a new once flag to use when it is created again.