Issue https://bugs.chromium.org/p/chromium/issues/detail?id=546206 changed the expected icon size for browser actions, but it was not reflected in documentation.

The documentation should state:
* the preferred size is now 16px and 32px instead of 19px and 38px
* the Chrome version that rolled the change out
* that old size icons are resized to fit, but should be updated

Affected documentation:
* https://developer.chrome.com/extensions/browserAction
* https://developer.chrome.com/extensions/pageAction
* https://developer.chrome.com/extensions/getstarted

Extension samples are also affected, though it's a lesser problem.