Move ownership of AppSorting from ExtensionPrefs to ExtensionSystem

extensions/browser/app_window/app_window_geometry_cache_unittest.cc

Index: extensions/browser/app_window/app_window_geometry_cache_unittest.cc
diff --git a/extensions/browser/app_window/app_window_geometry_cache_unittest.cc b/extensions/browser/app_window/app_window_geometry_cache_unittest.cc
index e1f4068440298217262576b2c982b80a4972d15f..234f1dcbbd67201094ebdf50894731ec34f28b98 100644
--- a/extensions/browser/app_window/app_window_geometry_cache_unittest.cc
+++ b/extensions/browser/app_window/app_window_geometry_cache_unittest.cc
@@ -17,7 +17,6 @@
 #include "extensions/browser/extension_pref_value_map.h"
 #include "extensions/browser/extension_prefs.h"
 #include "extensions/browser/extensions_test.h"
-#include "extensions/browser/null_app_sorting.h"
 #include "extensions/common/extension_builder.h"
 #include "extensions/common/value_builder.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -92,10 +91,10 @@ void AppWindowGeometryCacheTest::SetUp() {
   pref_service_ = factory.Create(pref_registry).Pass();
 
   extension_prefs_.reset(ExtensionPrefs::Create(
+      nullptr,

[not at google - send to devlin, 2015/08/03 21:12:08]

This seems to be the only case where ExtensionPrefs is created with a null
BrowserContext; and why does it need to be? You already have access to a
browser_context(), is there a reason you can't pass that through? If you do that
you can get rid of the null checks and the comments explaining the null
checks...

[Marc Treib, 2015/08/04 08:36:28]

D'oh, somehow I didn't see the |browser_context()| call right below here.
Passing it through now, and removed the null checks.

       pref_service_.get(),
       browser_context()->GetPath().AppendASCII("Extensions"),
       extension_pref_value_map_.get(),
-      scoped_ptr<AppSorting>(new NullAppSorting),
       false /* extensions_disabled */,
       std::vector<ExtensionPrefsObserver*>()));