Extract ErrorConsole from ExtensionSystem.

extensions/browser/extension_system.h

Index: extensions/browser/extension_system.h
diff --git a/extensions/browser/extension_system.h b/extensions/browser/extension_system.h
index 400f45e866734c14dba9cbc4d9a25e95ed6b8306..e5dd4680033c715d0feeb1f01c861fe38908d2bf 100644
--- a/extensions/browser/extension_system.h
+++ b/extensions/browser/extension_system.h
@@ -31,7 +31,6 @@ namespace extensions {
 
 class ContentVerifier;
 class DeclarativeUserScriptManager;
-class ErrorConsole;
 class EventRouter;
 class Extension;
 class ExtensionSet;
@@ -95,9 +94,6 @@ class ExtensionSystem : public KeyedService {
   // The EventRouter is created at startup.
   virtual EventRouter* event_router() = 0;
 
-  // The ErrorConsole is created at startup.
-  virtual ErrorConsole* error_console() = 0;
-
   // The InstallVerifier is created at startup.
   virtual InstallVerifier* install_verifier() = 0;