base::ReadFile() should return the number of read bytes on Windows.

base/file_util_posix.cc

Index: base/file_util_posix.cc
diff --git a/base/file_util_posix.cc b/base/file_util_posix.cc
index e2eb2f89ac09464bdb817c9798740b2979d149d3..73de948f6f65470f07d7877898956fcce03a4698 100644
--- a/base/file_util_posix.cc
+++ b/base/file_util_posix.cc
@@ -651,13 +651,13 @@ FILE* OpenFile(const FilePath& filename, const char* mode) {
   return result;
 }
 
-int ReadFile(const FilePath& filename, char* data, int size) {
+int ReadFile(const FilePath& filename, char* data, int max_size) {
   ThreadRestrictions::AssertIOAllowed();
   int fd = HANDLE_EINTR(open(filename.value().c_str(), O_RDONLY));
   if (fd < 0)
     return -1;
 
-  ssize_t bytes_read = HANDLE_EINTR(read(fd, data, size));
+  ssize_t bytes_read = HANDLE_EINTR(read(fd, data, max_size));

[Mark Mentovai, 2014/04/17 16:21:57]

I kinda feel like if this was a short read but EOF is not indicated, the read
should be retried until the buffer is full or the file is at EOF. We could do
this with ReadFromFD, but ReadFromFD doesn’t distinguish errors from EOF in its
return value.

I know it seems silly because this function looks like it works with regular
files (it accepts a filename argument that it opens, not an FD), and regular
files don’t usually result in short reads. Be mindful that the path may actually
name a special file (like a named pipe or a device file) that read short, and
even something that appears as a regular file may be on a filesystem that can
read short, such as a network filesystem or something like procfs.

[fukino, 2014/04/18 02:22:12]

Thank you for suggestion!
I didn't realize any cases you mentioned.
It's good lesson to me, but I can't start implementing because I don't have
Windows environment for now.
I'm going to commit this CL without improvement, so I filed this improvement as
http://crbug.com/364762 not to forget it.

   if (int ret = IGNORE_EINTR(close(fd)) < 0)

[Mark Mentovai, 2014/04/17 16:21:57]

You don’t need to track |ret| here, you can just

  if (IGNORE_EINTR(close(fd)) < 0)
    return -1;

[fukino, 2014/04/18 02:22:12]

Done for ReadFile(), WriteFile() and AppendToFile()

     return ret;
   return bytes_read;