Purge browser cache for dom storage in a smarter way

content/browser/dom_storage/dom_storage_namespace.h

Index: content/browser/dom_storage/dom_storage_namespace.h
diff --git a/content/browser/dom_storage/dom_storage_namespace.h b/content/browser/dom_storage/dom_storage_namespace.h
index fc091ede73b68aa9f13d1eda56d15fcb349b7ef7..1a589c9443a9d48ecba222bbbfb049545d7b60cd 100644
--- a/content/browser/dom_storage/dom_storage_namespace.h
+++ b/content/browser/dom_storage/dom_storage_namespace.h
@@ -34,6 +34,9 @@ class CONTENT_EXPORT DOMStorageNamespace
  public:
   // Option for PurgeMemory.
   enum PurgeOption {
+    // Determines the level of purging based on the usage and the platform.
+    PURGE_UNSPECIFIED,
+
     // Purge unopened areas only.
     PURGE_UNOPENED,
 
@@ -80,8 +83,6 @@ class CONTENT_EXPORT DOMStorageNamespace
   void Shutdown();
   void Flush();
 
-  unsigned int CountInMemoryAreas() const;
-
   // Adds memory statistics to |pmd| for chrome://tracing.
   void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd);
 
@@ -105,12 +106,16 @@ class CONTENT_EXPORT DOMStorageNamespace
   // Returns a pointer to the area holder in our map or NULL.
   AreaHolder* GetAreaHolder(const GURL& origin);
 
+  // Helper to determine the purging level based on the usage and the platform.
+  PurgeOption FindPurgeLevel();
+
   int64_t namespace_id_;
   std::string persistent_namespace_id_;
   base::FilePath directory_;
   AreaMap areas_;
   scoped_refptr<DOMStorageTaskRunner> task_runner_;
   scoped_refptr<SessionStorageDatabase> session_storage_database_;
+  bool is_low_end_device_;
 };
 
 }  // namespace content