Quota: Factor out (Mock)QuotaManagerProxy into its own file for readability

webkit/browser/appcache/appcache_service.h

Index: webkit/browser/appcache/appcache_service.h
diff --git a/webkit/browser/appcache/appcache_service.h b/webkit/browser/appcache/appcache_service.h
index 43e38b47b58ae45f257bf739e6774195930e51bc..51647d1b46f76153cb6fc509a11099922d0d2782 100644
--- a/webkit/browser/appcache/appcache_service.h
+++ b/webkit/browser/appcache/appcache_service.h
@@ -15,6 +15,7 @@
 #include "net/base/completion_callback.h"
 #include "net/base/net_errors.h"
 #include "webkit/browser/appcache/appcache_storage.h"
+#include "webkit/browser/quota/quota_manager_proxy.h"
 #include "webkit/browser/webkit_storage_browser_export.h"
 #include "webkit/common/appcache/appcache_interfaces.h"
 
@@ -28,7 +29,6 @@ class MessageLoopProxy;
 }
 
 namespace quota {
-class QuotaManagerProxy;
 class SpecialStoragePolicy;
 }