Enable login screen apps.

chrome/browser/extensions/installed_loader.cc

Index: chrome/browser/extensions/installed_loader.cc
diff --git a/chrome/browser/extensions/installed_loader.cc b/chrome/browser/extensions/installed_loader.cc
index 4f3cf1bec413ebf5f774f03334147a1a082f12cc..6e6fd2fcca827e3ebbe1166b7a7433f8a796df74 100644
--- a/chrome/browser/extensions/installed_loader.cc
+++ b/chrome/browser/extensions/installed_loader.cc
@@ -42,6 +42,10 @@
 #include "extensions/common/manifest_handlers/background_info.h"
 #include "extensions/common/manifest_url_handlers.h"
 
+#if defined(OS_CHROMEOS)
+#include "chrome/browser/chromeos/profiles/profile_helper.h"
+#endif
+
 using base::UserMetricsAction;
 using content::BrowserThread;
 
@@ -307,6 +311,11 @@ void InstalledLoader::LoadAllExtensions() {
   }
 
   for (size_t i = 0; i < extensions_info->size(); ++i) {
+#if defined(OS_CHROMEOS)
+    // Don't load saved extensions in signin profile.

[Devlin, 2017/03/08 17:24:32]

This seems like the wrong place to put this... we should probably just not call
LoadAllExtensions().  Ideally, we'd even avoid saving any in the profile, but
that might break stuff.

[achuithb, 2017/03/09 14:31:06]

I've tried to keep as much of the old behavior as possible. This function
LoadAllExtensions is doing a bunch of stuff, and I can't imagine it's safe to
simply not call it.

The model I've used here is that of extensions previously loaded via command
line. These are still saved, but not loaded on restart, which is exactly the
behavior we want for signin profile apps. I've modified this code to make that a
little clearer. PTAL.

[Devlin, 2017/03/13 19:39:35]

LoadAllExtensions() basically iterates over the profile prefs, grabs the
extensions mentioned there, and tries to load them.  For a signin profile, do we
want to persist these preferences?  Does the signin profile have stored state?

Additionally, this isn't quite the same as command line extensions, since that's
a per-extension decision, whereas this is a per-profile decision.

[achuithb, 2017/03/15 00:40:25]

There's state in the signin profile - for example the list of signed in users,
the network connection, language/keyboard, accessibility settings (high
contrast, large cursor), etc. I'm not 100% sure if these are stored as
preferences or in Local State. Even though the signin profile is not associated
with a particular user, it's not an incognito profile.

+    if (chromeos::ProfileHelper::IsSigninProfile(profile))
+      break;
+#endif
     if (extensions_info->at(i)->extension_location != Manifest::COMMAND_LINE)
       Load(*extensions_info->at(i), should_write_prefs);
   }