Add options for audio/video autoplay to chrome://settings/content.

components/content_settings/core/browser/content_settings_registry.cc

Index: components/content_settings/core/browser/content_settings_registry.cc
diff --git a/components/content_settings/core/browser/content_settings_registry.cc b/components/content_settings/core/browser/content_settings_registry.cc
index 28b46b6264db446c69041a228043857c1ee45a09..5febaebaee59b041bcaad0fc6422e22bb4054c91 100644
--- a/components/content_settings/core/browser/content_settings_registry.cc
+++ b/components/content_settings/core/browser/content_settings_registry.cc
@@ -228,6 +228,13 @@ void ContentSettingsRegistry::Init() {
            WhitelistedSchemes(),
            ValidSettings(CONTENT_SETTING_ALLOW, CONTENT_SETTING_BLOCK));
 
+  Register(CONTENT_SETTINGS_TYPE_MEDIA_AUTOPLAY, "media-autoplay",
+           CONTENT_SETTING_DETECT_IMPORTANT_CONTENT,
+           WebsiteSettingsInfo::SYNCABLE, WhitelistedSchemes(),

[raymes, 2015/10/27 23:34:51]

Do we really want this setting sync'd across devices?

[DaleCurtis, 2015/10/27 23:38:31]

Hmm, possibly not since Android would default to CONTENT_SETTING_BLOCK while
desktop would default to CONTENT_SETTING_DETECT_IMPORTANT_CONTENT. If
CONTENT_SETTING_DEFAULT is  what is actually sync'd then that's okay since we
can just control the default at runtime.

This is a good question for the eventual UX/UI review.

[felt, 2015/10/28 07:52:45]

My $0.02: the fact that there are different defaults implies that we think
people will want different things across device types. So syncing it seems odd.

[msramek, 2015/10/28 10:42:50]

Note that content settings are currently not synced to Android, so technically
it's not a problem. But I agree with the sentiment.

Another argument for NOT syncing is consistency with existing media-related
content settings (mic & camera).

[Bernhard Bauer, 2015/10/28 12:52:58]

It kind of sounds to me like what we want here is actually syncing, but with
separate settings for Android vs. desktop. There is no reason why I should have
to configure my settings again on an additional desktop or Android device.

+           ValidSettings(CONTENT_SETTING_ALLOW,
+                         CONTENT_SETTING_DETECT_IMPORTANT_CONTENT,
+                         CONTENT_SETTING_BLOCK));
+
   // Content settings that aren't used to store any data. TODO(raymes): use a
   // different mechanism rather than content settings to represent these.
   // Since nothing is stored in them, there is no real point in them being a