Split ValueSerializer into separate Serializer and Deserializer classes.

base/values.h

Index: base/values.h
diff --git a/base/values.h b/base/values.h
index 4648283a78af85e341858655bbff4bb013b9dc67..1e1cae3a9a93efaeaa0cc46feb71a8c6d19b2890 100644
--- a/base/values.h
+++ b/base/values.h
@@ -492,13 +492,20 @@ class BASE_EXPORT ListValue : public Value {
   DISALLOW_COPY_AND_ASSIGN(ListValue);
 };
 
-// This interface is implemented by classes that know how to serialize and
-// deserialize Value objects.
+// This interface is implemented by classes that know how to serialize
+// Value objects.
 class BASE_EXPORT ValueSerializer {
  public:
   virtual ~ValueSerializer();
 
   virtual bool Serialize(const Value& root) = 0;
+};
+
+// This interface is implemented by classes that know how to deserialize Value
+// objects.
+class BASE_EXPORT ValueDeserializer {
+ public:
+  virtual ~ValueDeserializer();
 
   // This method deserializes the subclass-specific format into a Value object.
   // If the return value is non-NULL, the caller takes ownership of returned