Some fleshing out the mojo based localstorage implementation.

content/common/leveldb_wrapper.mojom

Index: content/common/leveldb_wrapper.mojom
diff --git a/content/common/leveldb_wrapper.mojom b/content/common/leveldb_wrapper.mojom
index 27ad0cba2e59c00a46822903ee24b9293679b3d7..91c12f5f25a0a1b95e38d31cadd645826dfa2544 100644
--- a/content/common/leveldb_wrapper.mojom
+++ b/content/common/leveldb_wrapper.mojom
@@ -16,10 +16,12 @@ import "components/leveldb/public/interfaces/leveldb.mojom";
 // Note that observer methods are called before the callbacks for the
 // LevelDBWrapper methods are run.
 interface LevelDBObserver {
+  KeyAdded(array<uint8> key, array<uint8> value, string source);
   KeyChanged(array<uint8> key, array<uint8> new_value, array<uint8> old_value,
              string source);
   KeyDeleted(array<uint8> key, array<uint8> old_value, string source);
   AllDeleted(string source);
+  GetAllComplete(uint64 request_id);
 };
 
 struct KeyValue {
@@ -30,24 +32,21 @@ struct KeyValue {
 // A wrapper around leveldb that supports giving notifications when values
 // change.
 interface LevelDBWrapper {
+  AddObserver(LevelDBObserver observer);
+
   // Sets the database entry for |key| to |value|. Returns OK on success.
-  Put(array<uint8> key, array<uint8> value, string source)
-    => (leveldb.DatabaseError status);
+  Put(array<uint8> key, array<uint8> value, string source) => (bool success);
 
   // Remove the database entry (if any) for |key|.  Returns OK on success, and a
   // non-OK status on error.  It is not an error if |key| did not exist in the
   // database.
-  Delete(array<uint8> key, string source) => (leveldb.DatabaseError status);
+  Delete(array<uint8> key, string source) => (bool success);
 
   // Removes all the entries.
-  DeleteAll(LevelDBObserver observer, string source)
-    => (leveldb.DatabaseError status);
-
-  // Returns the value of the |key|.
-  Get(array<uint8> key) => (leveldb.DatabaseError status, array<uint8> value);
+  DeleteAll(string source) => (bool success);
 
   // Only used with small databases. Returns all key/value pairs.
   [Sync]
-  GetAll(LevelDBObserver observer)
+  GetAll(uint64 reqeust_id)
     => (leveldb.DatabaseError status, array<KeyValue> data);
 };