Purge browser cache for dom storage in a smarter way

content/browser/dom_storage/dom_storage_context_impl.h

Index: content/browser/dom_storage/dom_storage_context_impl.h
diff --git a/content/browser/dom_storage/dom_storage_context_impl.h b/content/browser/dom_storage/dom_storage_context_impl.h
index c2bbe4d42b50fcd2991e976540e64a6e1b58acc0..c8f27e37ed8cb355852264ac7d32ca90192cfe80 100644
--- a/content/browser/dom_storage/dom_storage_context_impl.h
+++ b/content/browser/dom_storage/dom_storage_context_impl.h
@@ -65,6 +65,9 @@ class CONTENT_EXPORT DOMStorageContextImpl
     : public base::RefCountedThreadSafe<DOMStorageContextImpl>,
       public base::trace_event::MemoryDumpProvider {
  public:
+  typedef std::map<int64_t, scoped_refptr<DOMStorageNamespace>>
+      StorageNamespaceMap;
+
   // An interface for observing Local and Session Storage events on the
   // background thread.
   class EventObserver {
@@ -89,6 +92,19 @@ class CONTENT_EXPORT DOMStorageContextImpl
     virtual ~EventObserver() {}
   };
 
+  // Option for PurgeMemory.
+  enum PurgeOption {
+    // Determines if purging is required based on the usage and the platform.
+    PURGE_IF_NEEDED,
+
+    // Purge unopened areas only.
+    PURGE_UNOPENED,
+
+    // Purge aggressively, i.e. discard cache even for areas that have
+    // non-zero open count.
+    PURGE_AGGRESSIVE,
+  };
+
   // |localstorage_directory| and |sessionstorage_directory| may be empty
   // for incognito browser contexts.
   DOMStorageContextImpl(const base::FilePath& localstorage_directory,
@@ -175,6 +191,10 @@ class CONTENT_EXPORT DOMStorageContextImpl
   // unclean exit.
   void StartScavengingUnusedSessionStorage();
 
+  // Frees up memory when possible. Purges caches and schedules commits
+  // depending on the given |purge_option|.
+  void PurgeMemory(PurgeOption purge_option);
+
   // base::trace_event::MemoryDumpProvider implementation.
   bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
                     base::trace_event::ProcessMemoryDump* pmd) override;
@@ -183,8 +203,6 @@ class CONTENT_EXPORT DOMStorageContextImpl
   friend class DOMStorageContextImplTest;
   FRIEND_TEST_ALL_PREFIXES(DOMStorageContextImplTest, Basics);
   friend class base::RefCountedThreadSafe<DOMStorageContextImpl>;
-  typedef std::map<int64_t, scoped_refptr<DOMStorageNamespace>>
-      StorageNamespaceMap;
 
   ~DOMStorageContextImpl() override;
 
@@ -238,6 +256,9 @@ class CONTENT_EXPORT DOMStorageContextImpl
   // Mapping between persistent namespace IDs and namespace IDs for
   // sessionStorage.
   std::map<std::string, int64_t> persistent_namespace_id_to_namespace_id_;
+
+  // For cleaning up unused databases more aggressively.
+  bool is_low_end_device_;
 };
 
 }  // namespace content