Return true when file size is zero.

base/test/test_file_util_mac.cc

Index: base/test/test_file_util_mac.cc
diff --git a/base/test/test_file_util_mac.cc b/base/test/test_file_util_mac.cc
index 316b5c3d01aa9aec7c42d64bce64be95cd0b0969..7d01db2fa0c5af2bbdb712e41dad1c85ceb0d408 100644
--- a/base/test/test_file_util_mac.cc
+++ b/base/test/test_file_util_mac.cc
@@ -17,6 +17,16 @@ bool EvictFileFromSystemCache(const FilePath& file) {
   // default) + MAP_SHARED, then do an msync to invalidate the memory.  The next
   // open should then have to load the file from disk.
 
+  int64 length;
+  if (!file_util::GetFileSize(file, &length)) {

[kkania, 2011/07/23 00:27:02]

now that I think about it, I'm not sure this is correct. If you don't evict from
the cache and the file changes, will later reads possibly still see the empty
file? Or is an empty file not in the cache to begin with?

[TVL, 2011/07/25 12:40:10]

If the OS cache had that sort of bugs/behaviors, you can assume all sorts of
things would probably go wrong.  In this case, since the file is zero sized,
there really isn't anything for it to have cached.

+    DLOG(WARNING) << "failed to get size of " << file.value();
+    return false;
+  }
+
+  // When a file is empty, we do not need to purge it.

[kkania, 2011/07/23 00:23:31]

maybe include that mapping it would cause an error?

+  if (!length)
+    return true;
+
   file_util::MemoryMappedFile mapped_file;
   if (!mapped_file.Initialize(file)) {
     DLOG(WARNING) << "failed to memory map " << file.value();