Cleanup: give ChromeAppSorting a BrowserContext

extensions/browser/extensions_browser_client.h

Index: extensions/browser/extensions_browser_client.h
diff --git a/extensions/browser/extensions_browser_client.h b/extensions/browser/extensions_browser_client.h
index 4aefa37e7ad8759f3364511488ca206965b96334..5c52a1cb9c5c009d0ae15207bcf2cd051e347870 100644
--- a/extensions/browser/extensions_browser_client.h
+++ b/extensions/browser/extensions_browser_client.h
@@ -161,7 +161,8 @@ class ExtensionsBrowserClient {
   virtual void PermitExternalProtocolHandler() = 0;
 
   // Creates a new AppSorting instance.
-  virtual scoped_ptr<AppSorting> CreateAppSorting() = 0;
+  virtual scoped_ptr<AppSorting> CreateAppSorting(

[not at google - send to devlin, 2015/07/23 15:35:11]

Even more cleanup:

This stuff would all be much simpler if there were an "app_sorting()" method on
ExtensionSystem, which ExtensionSystemImpl overrides to return a
ChromeAppSorting, and everything else returns a NullAppSorting/nullptr (and why
are both acceptable? eh whatever).

I.e. shift ownership of AppSorting from ExtensionPrefs to ExtensionSystem.

That would let you delete AppSorting::SetExtensionScopedPrefs, and instead
ChromeAppSorting could just retrieve the ExtensionPrefs instance from the
BrowserContext it's given.

It would also let you simply delete ExtensionsBrowserClient::CreateAppSorting
rather than updating it.

[Marc Treib, 2015/07/24 11:38:34]

I started on this, but then realized it creates a dependency cycle:
ExtensionSystem depends on ExtensionPrefs, but ExtensionPrefs needs an
AppSorting and so now will depend on ExtensionSystem. That could probably be
worked around with an ExtensionPrefs::set_app_sorting or something like that,
but then we won't really win much by the whole thing. WDYT?

[not at google - send to devlin, 2015/07/24 14:43:53]

That's pretty typical, usually all these things depend on in their constructor
is a Profile/BrowserContext. They fetch the ExtensionPrefs/AppSorting from that,
sometimes via an ExtensionSystem, when needed.

+      content::BrowserContext* context) = 0;
 
   // Return true if the system is run in forced app mode.
   virtual bool IsRunningInForcedAppMode() = 0;