[BlobAsync] Disk support for blob storage

storage/browser/blob/shareable_blob_data_item.h

Index: storage/browser/blob/shareable_blob_data_item.h
diff --git a/storage/browser/blob/shareable_blob_data_item.h b/storage/browser/blob/shareable_blob_data_item.h
index 4c2f9c1833262d18dfa82b622abdfef8585b9541..6ab1b18bd3b0a84cba4287bf1a01c652cf126b0d 100644
--- a/storage/browser/blob/shareable_blob_data_item.h
+++ b/storage/browser/blob/shareable_blob_data_item.h
@@ -11,6 +11,7 @@
 #include "base/hash.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "storage/browser/storage_browser_export.h"
 #include "storage/common/data_element.h"
 
 namespace storage {
@@ -23,22 +24,34 @@ class InternalBlobData;
 // The data in this class (the item) is immutable, but the item itself can be
 // swapped out with an item with the same data but a different backing (think
 // RAM vs file backed).
-class ShareableBlobDataItem : public base::RefCounted<ShareableBlobDataItem> {
+class STORAGE_EXPORT ShareableBlobDataItem
+    : public base::RefCountedThreadSafe<ShareableBlobDataItem> {
  public:
-  ShareableBlobDataItem(const std::string& blob_uuid,
-                        const scoped_refptr<BlobDataItem>& item);
+  ShareableBlobDataItem(scoped_refptr<BlobDataItem> item);
 
-  const scoped_refptr<BlobDataItem>& item();
+  const scoped_refptr<BlobDataItem>& item() const;
 
-  base::hash_set<std::string>& referencing_blobs() {
+  // This is a unique auto-incrementing id assigned to this item on
+  // construction. It is used to keep track of this item in an LRU data
+  // structure for eviction to disk.
+  uint64_t item_id() const { return item_id_; }
+
+  const base::hash_set<std::string>& referencing_blobs() const {
     return referencing_blobs_;
   }
 
  private:
-  friend class base::RefCounted<ShareableBlobDataItem>;
+  friend class base::RefCountedThreadSafe<ShareableBlobDataItem>;
   friend class InternalBlobData;
+  friend class BlobMemoryController;
+  friend class BlobStorageContext;
+  friend STORAGE_EXPORT void PrintTo(const ShareableBlobDataItem& x,
+                                     ::std::ostream* os);
+
   ~ShareableBlobDataItem();
 
+  // This is a unique identifier for this ShareableBlobDataItem.
+  uint64_t item_id_;
   scoped_refptr<BlobDataItem> item_;
 
   base::hash_set<std::string> referencing_blobs_;
@@ -46,5 +59,10 @@ class ShareableBlobDataItem : public base::RefCounted<ShareableBlobDataItem> {
   DISALLOW_COPY_AND_ASSIGN(ShareableBlobDataItem);
 };
 
+STORAGE_EXPORT bool operator==(const ShareableBlobDataItem& a,
+                               const ShareableBlobDataItem& b);
+STORAGE_EXPORT bool operator!=(const ShareableBlobDataItem& a,
+                               const ShareableBlobDataItem& b);
+
 }  // namespace storage
 #endif  // STORAGE_BROWSER_BLOB_SHAREABLE_BLOB_DATA_ITEM_H_