Здравствуйте,
мне необходимо включить модальные окна в браузере.
Здесь http://www.chromium.org/administrators/policy-list-3 я нашел политику:

EnableDeprecatedWebPlatformFeatures

Enable deprecated web platform features for a limited time
Data type:
List of strings
Windows registry location:
Software\Policies\Chromium\EnableDeprecatedWebPlatformFeatures
Mac/Linux preference name:
EnableDeprecatedWebPlatformFeatures
Supported on:
Chromium (Linux, Mac, Windows) since version 37
Chromium OS (Chromium OS) since version 37
Chromium (Android) since version 37
Supported features:
Dynamic Policy Refresh: Yes, Per Profile: Yes
Description:
Specify a list of deprecated web platform features to re-enable temporarily. This policy gives administrators the ability to re-enable deprecated web platform features for a limited time. Features are identified by a string tag and the features corresponding to the tags included in the list specified by this policy will get re-enabled. If this policy is left not set, or the list is empty or does not match one of the supported string tags, all deprecated web platform features will remain disabled. While the policy itself is supported on the above platforms, the feature it is enabling may be available on fewer platforms. Not all deprecated Web Platform features can be re-enabled. Only the ones explicitly listed below can be for a limited period of time, which is different per feature. The general format of the string tag will be [DeprecatedFeatureName]_EffectiveUntil[yyyymmdd]. As reference, you can find the intent behind the Web Platform feature changes at http://bit.ly/blinkintents.
"ShowModalDialog_EffectiveUntil20150430" = Enable ShowModalDialog API through 2015.04.30
Example value:
Windows:
Software\Policies\Chromium\EnableDeprecatedWebPlatformFeatures\1 = "ShowModalDialog_EffectiveUntil20150430"
Linux:
["ShowModalDialog_EffectiveUntil20150430"]
Mac:
<array>
<string>ShowModalDialog_EffectiveUntil20150430</string>

По этой инструкции http://www.chromium.org/administrators/linux-quick-start
я создал json-файл со следующим содержимым:
"{
["ShowModalDialog_EffectiveUntil20150430"]
}"