Add MinidumpMemoryWriter, MinidumpMemoryListWriter, and their test

minidump/minidump_writable.h

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 241 matching lines @@
   //! \param[in] file_writer The file writer to receive the object’s content.
   //!
   //! \return `true` on success. `false` on error, indicating that the content
   //!     could not be written to the minidump file.
   //!
   //! \note Valid in #kStateWritable. The object will transition to
   //!     #kStateWritten after this method returns.
   virtual bool WriteObject(FileWriterInterface* file_writer) = 0;
 
  private:
-  std::vector<RVA*> registered_rvas_;
+  std::vector<RVA*> registered_rvas_;  // weak
+
+  // weak
   std::vector<MINIDUMP_LOCATION_DESCRIPTOR*> registered_location_descriptors_;
+
   size_t leading_pad_bytes_;
   State state_;
 
   DISALLOW_COPY_AND_ASSIGN(MinidumpWritable);
 };
 
 }  // namespace internal
 }  // namespace crashpad
 
 #endif  // CRASHPAD_MINIDUMP_MINIDUMP_WRITABLE_H_