Allow passing in strings of length zero to FileWrapper::Write without closing the file.

webrtc/system_wrappers/source/file_impl.cc

Index: webrtc/system_wrappers/source/file_impl.cc
diff --git a/webrtc/system_wrappers/source/file_impl.cc b/webrtc/system_wrappers/source/file_impl.cc
index 0ee0deab6c1061edb3f475d44a3ff9b7e6f7f51d..e033c0eb7347f86227d0114e24b74fcf4502dd45 100644
--- a/webrtc/system_wrappers/source/file_impl.cc
+++ b/webrtc/system_wrappers/source/file_impl.cc
@@ -243,13 +243,12 @@ bool FileWrapperImpl::Write(const void* buf, size_t length) {
   }
 
   size_t num_bytes = fwrite(buf, 1, length, id_);
-  if (num_bytes > 0) {
-    size_in_bytes_ += num_bytes;
-    return true;
+  size_in_bytes_ += num_bytes;
+  if (num_bytes != length) {
+    CloseFileImpl();
+    return false;
   }
-
-  CloseFileImpl();
-  return false;
+  return true;
 }
 
 int FileWrapperImpl::CloseFileImpl() {