Add FileReaderInterface. Move StringFileWriter to StringFile and

util/file/file_writer.h

Index: util/file/file_writer.h
diff --git a/util/file/file_writer.h b/util/file/file_writer.h
index 62fddf5f37180ef39c78c3c6ecfeda726d6d30aa..f2bc452d9ca46acbcc3271d9873d351619d72e10 100644
--- a/util/file/file_writer.h
+++ b/util/file/file_writer.h
@@ -15,15 +15,12 @@
 #ifndef CRASHPAD_UTIL_FILE_FILE_WRITER_H_
 #define CRASHPAD_UTIL_FILE_FILE_WRITER_H_
 
-#include <fcntl.h>
-#include <stddef.h>
+#include <sys/types.h>
 
-#include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/files/file_path.h"
-#include "build/build_config.h"
 #include "util/file/file_io.h"
 
 namespace crashpad {
@@ -44,6 +41,8 @@ struct WritableIoVec {
 
 //! \brief An interface to write to files and other file-like objects with
 //!     semantics matching the underlying platform (POSIX or Windows).
+//
+// TODO(mark): Templatize and share more with FileReaderInterface?
 class FileWriterInterface {
  public:
   //! \brief Wraps WriteFile(), or provides an implementation with identical
@@ -69,6 +68,9 @@ class FileWriterInterface {
   //!
   //! \return The return value of LoggingFileSeek(). `-1` on failure,
   //!     with an error message logged.
+  //
+  // TODO(mark): This may be better with a common base of FileWriterInterface
+  // and FileReaderInterface to declaring Seek().
   virtual FileOffset Seek(FileOffset offset, int whence) = 0;
 
  protected:
@@ -110,7 +112,7 @@ class WeakFileHandleFileWriter : public FileWriterInterface {
   FileHandle file_handle_;  // weak
 
   // FileWriter uses this class as its internal implementation, and it needs to
-  // be able to call set_file_handle(). FileWriter cannot initialize an
+  // be able to call set_file_handle(). FileWriter cannot initialize a
   // WeakFileHandleFileWriter with a correct file descriptor at the time of
   // construction because no file descriptor will be available until
   // FileWriter::Open() is called.