Output from the Editor/Player that goes to Editor.log or Player.log is printed one byte at a time.

Steps to reproduce:
1) Open the latest attached project (TestLogging.zip).
2) Download and open ProcessMonitor (https://technet.microsoft.com/en-us/sysinternals/processmonitor.aspx).
3) In ProcessMonitor, add a filter for Operation: "QueryStandardInformationFile" and Process: "Unity.exe".
4) Enter play mode in Unity.
5) Press any key.

Notice that around 200 calls (depending on the message length - one call for each char) to QueryStandardInformationFile appear in ProcessMonitor. This means that the text is output to the log one byte at a time.

The same issue occurs with Player logs.
This does not reproduce on macOS (tested using fs_usage command).

Expected: the whole message is logged at once.
Actual: the message is logged one byte at a time.

Reproduced on:
5.6.0b6, 5.4.4p1, 5.2.4f1

Tested on: Windows 10, macOS 10.12.3