Align IndexedDB metadata rollback on transaction abort to spec.

third_party/WebKit/Source/modules/indexeddb/IDBMetadata.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 15 matching lines @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef IDBMetadata_h
 #define IDBMetadata_h
 
 #include "modules/indexeddb/IDBKeyPath.h"
 #include "public/platform/modules/indexeddb/WebIDBMetadata.h"
 #include "wtf/Allocator.h"
 #include "wtf/HashMap.h"
+#include "wtf/RefCounted.h"
+#include "wtf/RefPtr.h"
 #include "wtf/text/StringHash.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
-struct IDBIndexMetadata {
-  DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
-  IDBIndexMetadata() {}
+// The lifecycle of the IndexedDB metadata objects defined below is managed by
+// reference counting (RefPtr). We don't have to worry about cycles because
+// these objects form a tree with the hierarch shown below.

[jsbell, 2016/10/06 20:01:31]

typo: hierarchy

[pwnall, 2016/10/06 22:15:22]

Done.
Gah... I swore I fixed this when addressing cmumford's feedback. Sorry, and
thank you so much for catching my mistake!

+//     IDBDatabaseMetadata -> IDBObjectStoreMetadata -> IDBIndexMetadata
+
+class IDBIndexMetadata : public RefCounted<IDBIndexMetadata> {
+  USING_FAST_MALLOC(IDBIndexMetadata);
+
+ public:
+  static constexpr int64_t InvalidId = -1;
+
+  IDBIndexMetadata();
   IDBIndexMetadata(const String& name,
                    int64_t id,
-                   const IDBKeyPath& keyPath,
+                   const IDBKeyPath&,
                    bool unique,
-                   bool multiEntry)
-      : name(name),
-        id(id),
-        keyPath(keyPath),
-        unique(unique),
-        multiEntry(multiEntry) {}
+                   bool multiEntry);
+
   String name;
   int64_t id;
   IDBKeyPath keyPath;
   bool unique;
   bool multiEntry;
-
-  static constexpr int64_t InvalidId = -1;
 };
 
-struct IDBObjectStoreMetadata {
-  DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
-  IDBObjectStoreMetadata() {}
+class IDBObjectStoreMetadata : public RefCounted<IDBObjectStoreMetadata> {
+  USING_FAST_MALLOC(IDBObjectStoreMetadata);
+
+ public:
+  static constexpr int64_t InvalidId = -1;
+
+  IDBObjectStoreMetadata();
   IDBObjectStoreMetadata(const String& name,
                          int64_t id,
-                         const IDBKeyPath& keyPath,
+                         const IDBKeyPath&,
                          bool autoIncrement,
-                         int64_t maxIndexId)
-      : name(name),
-        id(id),
-        keyPath(keyPath),
-        autoIncrement(autoIncrement),
-        maxIndexId(maxIndexId) {}
+                         int64_t maxIndexId);
+
+  // Creates a deep copy of the object metadata, which includes copies of index
+  // metadata items.
+  RefPtr<IDBObjectStoreMetadata> createCopy() const;
+
   String name;
   int64_t id;
   IDBKeyPath keyPath;
   bool autoIncrement;
   int64_t maxIndexId;
-
-  static constexpr int64_t InvalidId = -1;
-
-  typedef HashMap<int64_t, IDBIndexMetadata> IndexMap;
-  IndexMap indexes;
+  HashMap<int64_t, RefPtr<IDBIndexMetadata>> indexes;
 };
 
-struct IDBDatabaseMetadata {
+struct MODULES_EXPORT IDBDatabaseMetadata {
   DISALLOW_NEW();
+
   // FIXME: These can probably be collapsed into 0.
   enum { NoVersion = -1, DefaultVersion = 0 };
 
-  typedef HashMap<int64_t, IDBObjectStoreMetadata> ObjectStoreMap;
-
-  IDBDatabaseMetadata() : version(NoVersion) {}
-
+  IDBDatabaseMetadata();
   IDBDatabaseMetadata(const String& name,
                       int64_t id,
                       int64_t version,
-                      int64_t maxObjectStoreId)
-      : name(name),
-        id(id),
-        version(version),
-        maxObjectStoreId(maxObjectStoreId) {}
+                      int64_t maxObjectStoreId);
 
   explicit IDBDatabaseMetadata(const WebIDBMetadata&);
 
+  // Overwrites the database metadata, but does not change the object store and
+  // index metadata.
+  void copyDatabaseMetadataFrom(const IDBDatabaseMetadata&);

[jsbell, 2016/10/06 20:01:31]

Simplify to just 'copyFrom' ?

[pwnall, 2016/10/06 22:15:22]

Done.
FWIW, I think that copyFrom is a bit of a lie, because we don't copy store
metadata, but the name I had before isn't any better. Thank you!

+
   String name;
   int64_t id;
   int64_t version;
   int64_t maxObjectStoreId;
-
-  ObjectStoreMap objectStores;
+  HashMap<int64_t, RefPtr<IDBObjectStoreMetadata>> objectStores;
 };
 
 }  // namespace blink
 
 #endif  // IDBMetadata_h