[Extensions] Make extension message bubble factory platform-abstract

chrome/browser/ui/extensions/OWNERS

Index: chrome/browser/ui/extensions/OWNERS
diff --git a/chrome/browser/ui/extensions/OWNERS b/chrome/browser/ui/extensions/OWNERS
index 98867c413c705afd917064a91868919c64864194..fbf229bd15d2460faae78668e95bbf7666e0a7c7 100644
--- a/chrome/browser/ui/extensions/OWNERS
+++ b/chrome/browser/ui/extensions/OWNERS
@@ -2,5 +2,5 @@ benwells@chromium.org
 miket@chromium.org
 
 # Extension/Toolbar Actions Files
-per-file extension_action*=finnur@chromium.org
-per-file extension_action*=rdevlin.cronin@chromium.org
+per-file extension*=finnur@chromium.org
+per-file extension*=rdevlin.cronin@chromium.org

[Devlin, 2015/04/10 00:30:13]

Also lemme know if you're okay with this - after a bit of thought, it seems more
appropriate (to grasp this, the install ui, etc).  I'll run it by Scott if you
think it's okay.

[Finnur, 2015/04/10 11:24:21]

The name for this directory is so general that I worry all kinds of crap is
going to be added to it that we probably shouldn't be owners of (even with the
limitation of the extension_ prefix, which is pretty general). Is there a
pattern to this that make sense to exploit (e.g. the ones related to install,
put them in a subdirectory 'install' so we don't have to take ownership of
future random stuff)? :)

[Devlin, 2015/04/10 15:55:19]

I think we try to avoid having really fine-grained directories (for better or
worse - I'd probably prefer it, but I see the advantage both ways, and best to
stick to the norm), so I think having a directory for "install" and a directory
for "bubble" and a directory for "extension_action" is probably wrong.  But
you're also definitely right that we don't want to accidentally end up owning
"random" stuff. :)

So, in lieu of that, I'd be inclined to say that a few extra lines in OWNERS
files is okay, and just add in explicit rules - it's still readable, and more
accurate overall. :)