Add MinidumpMemoryListWriter::AddFromSnapshot(), everything downstream and its test

minidump/minidump_memory_writer.h

Index: minidump/minidump_memory_writer.h
diff --git a/minidump/minidump_memory_writer.h b/minidump/minidump_memory_writer.h
index 369fafd90b27fd7f374bc6e6361c7512fec7ba1b..9cc4a060dccada0e237c256cae0691b681a1b0b9 100644
--- a/minidump/minidump_memory_writer.h
+++ b/minidump/minidump_memory_writer.h
@@ -29,6 +29,8 @@
 
 namespace crashpad {
 
+class MemorySnapshot;
+
 //! \brief The base class for writers of memory ranges pointed to by
 //!     MINIDUMP_MEMORY_DESCRIPTOR objects in a minidump file.
 //!
@@ -41,6 +43,16 @@ class MinidumpMemoryWriter : public internal::MinidumpWritable {
  public:
   ~MinidumpMemoryWriter() override;
 
+  //! \brief Creates a concrete initialized MinidumpMemoryWriter based on \a
+  //!     memory_snapshot.
+  //!
+  //! \param[in] memory_snapshot The memory snapshot to use as source data.
+  //!
+  //! \return An object of a MinidumpMemoryWriter subclass initialized using the
+  //!     source data in \a memory_snapshot.
+  static scoped_ptr<MinidumpMemoryWriter> CreateFromSnapshot(
+      const MemorySnapshot* memory_snapshot);
+
   //! \brief Returns a MINIDUMP_MEMORY_DESCRIPTOR referencing the data that this
   //!     object writes.
   //!
@@ -121,6 +133,17 @@ class MinidumpMemoryListWriter final : public internal::MinidumpStreamWriter {
   MinidumpMemoryListWriter();
   ~MinidumpMemoryListWriter() override;
 
+  //! \brief Adds a concrete initialized MinidumpMemoryWriter for each memory
+  //!     snapshot in \a memory_snapshots to the MINIDUMP_MEMORY_LIST.
+  //!
+  //! Memory snapshots are added in the fashion of AddMemory().
+  //!
+  //! \param[in] memory_snapshots The memory snapshots to use as source data.
+  //!
+  //! \note Valid in #kStateMutable.
+  void AddFromSnapshot(
+      const std::vector<const MemorySnapshot*>& memory_snapshots);
+
   //! \brief Adds a MinidumpMemoryWriter to the MINIDUMP_MEMORY_LIST.
   //!
   //! This object takes ownership of \a memory_writer and becomes its parent in