Create blobs from Disk Cache entries.

storage/common/data_element.h

Index: storage/common/data_element.h
diff --git a/storage/common/data_element.h b/storage/common/data_element.h
index 0efe1550a91e9a509d1cc0548854167a58c3a689..a35d29d74bfbeab57665196c25e7b220f4aa4c47 100644
--- a/storage/common/data_element.h
+++ b/storage/common/data_element.h
@@ -27,6 +27,7 @@ class STORAGE_COMMON_EXPORT DataElement {
     TYPE_FILE,
     TYPE_BLOB,
     TYPE_FILE_FILESYSTEM,
+    TYPE_DISK_CACHE_ENTRY,
   };
 
   DataElement();
@@ -102,6 +103,9 @@ class STORAGE_COMMON_EXPORT DataElement {
                                uint64 offset, uint64 length,
                                const base::Time& expected_modification_time);
 
+  // Sets to TYPE_DISK_CACHE_ENTRY with range.
+  void SetToDiskCacheEntryRange(uint64 offset, uint64 length);
+
  private:
   Type type_;
   std::vector<char> buf_;  // For TYPE_BYTES.
@@ -130,6 +134,12 @@ inline bool operator==(const DataElement& a, const DataElement& b) {
       return a.blob_uuid() == b.blob_uuid();
     case DataElement::TYPE_FILE_FILESYSTEM:
       return a.filesystem_url() == b.filesystem_url();
+    case DataElement::TYPE_DISK_CACHE_ENTRY:
+      // This comparison is really problematic; we could compare length and
+      // offset, but that would be deceptive: the disk cache entry itself can't
+      // be in the DataElement since it isn't serlializable. Thus, return |true|
+      // each time.
+      return true;
     case DataElement::TYPE_UNKNOWN:
       NOTREACHED();
       return false;