QuotaManager: Return the remaining free disk space as quota.

webkit/quota/special_storage_policy.h

Index: webkit/quota/special_storage_policy.h
diff --git a/webkit/quota/special_storage_policy.h b/webkit/quota/special_storage_policy.h
index f7d80f7de240155429d44dfd1cd91e736ebe2360..60ddaa03867c90a7bfc69ca8dab226f6652d2254 100644
--- a/webkit/quota/special_storage_policy.h
+++ b/webkit/quota/special_storage_policy.h
@@ -38,6 +38,9 @@ class SpecialStoragePolicy
   // Unlimited storage is not subject to 'quotas'.
   virtual bool IsStorageUnlimited(const GURL& origin) = 0;
 
+  // Installed apps have access to the size of the remaining disk capacity.
+  virtual bool IsInstalledApp(const GURL& origin) = 0;
+
   // Checks if extension identified with |extension_id| is registered as
   // file handler.
   virtual bool IsFileHandler(const std::string& extension_id) = 0;