This has been changed since v32, thanks to @Daniel Alexiuc & @Thanatos for their comments.
Current (≥ v32)
At the top of the "Network" tab of DevTools, there's a checkbox to switch on the "Preserve log" functionality. If it is checked, the network log is preserved on page load.
The little red dot on the left now has the purpose to switch network logging on and off completely.
Older versions
In older versions of Chrome (v21 here), there's a little, clickable red dot in the footer of the "Network" tab.
If you hover over it, it will tell you, that it will "Preserve Log Upon Navigation" when it is activated. It holds the promise.
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