vk.com, the biggest social network in Russia, hosts lots of Flash games via iframes that point to other domains. Despite vk.com is whitelisted for HBD, the Flash games are not activated by default. This looks like a HBD whitelisting bug to me.

Examples of games: https://vk.com/apps (most of them are in Russian though, e.g. https://vk.com/app5448769_340706016)

from chrome://version

Google Chrome	53.0.2785.116 (Official Build) (64-bit)
Revision	3f9c628bfd1de2c62de1ea41d0707d06cc760061-refs/branch-heads/2785@{#886}
OS	Mac OS X 
Blink	537.36 (@3f9c628bfd1de2c62de1ea41d0707d06cc760061)
JavaScript	V8 5.3.332.45
Flash	23.0.0.162
User Agent	Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36
Command Line	/Applications/Google Chrome.app/Contents/MacOS/Google Chrome --flag-switches-begin --enable-experimental-web-platform-features --flag-switches-end
Executable Path	/Applications/Google Chrome.app/Contents/MacOS/Google Chrome
Profile Path	/Users/nodir/Library/Application Support/Google/Chrome/Default
Variations	6a89113b-30be434a
b3888d8d-bb338302
6345b824-3d47f4f4
7c1bc906-f55a7974
1c752ce9-ca7d8d80
ba3f87da-ca7d8d80
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f15c1c09-ca7d8d80
9e5c75f1-c16ec2e6
f5dd6118-2f5721af
f79cb77b-3f4a17df
868bda90-ca7d8d80
4ea303a6-e25ec47e
9736de91-ca7d8d80
867c4c68-ca7d8d80
f47ae82a-86f22ee5
3ac60855-3ec2a267
f296190c-eaceac83
4442aae2-75cb33fc
ed1d377-e1cc0f14
75f0f0a0-a5822863
e2b18481-4ad60575
e7e71889-4ad60575